@JohnJ

Hi, I currently have the AX-53, though I am in NTSC land (U.S.). Here is a MediaInfo from a 4K clip:

General
Complete name                            : S:\Driving Fun from VA 20201217\AX-53\C0001.MP4
Format                                   : XAVC
Codec ID                                 : XAVC (XAVC/mp42/iso2)
File size                                : 1.03 GiB
Duration                                 : 1 min 29 s
Overall bit rate mode                    : Variable
Overall bit rate                         : 98.9 Mb/s
Encoded date                             : UTC 2020-12-17 16:41:24
Tagged date                              : UTC 2020-12-17 16:41:24

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L5.1
Format settings                          : CABAC / 2 Ref Frames
Format settings, CABAC                   : Yes
Format settings, Reference frames        : 2 frames
Codec ID                                 : avc1
Codec ID/Info                            : Advanced Video Coding
Duration                                 : 1 min 29 s
Bit rate mode                            : Variable
Bit rate                                 : 97.1 Mb/s
Maximum bit rate                         : 100.0 Mb/s
Width                                    : 3 840 pixels
Height                                   : 2 160 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 29.970 (30000/1001) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.391
Stream size                              : 1.01 GiB (98%)
Encoded date                             : UTC 2020-12-17 16:41:24
Tagged date                              : UTC 2020-12-17 16:41:24
Color range                              : Limited
Color primaries                          : BT.709
Transfer characteristics                 : xvYCC
Matrix coefficients                      : BT.709
Metas                                    : 3
Codec configuration box                  : avcC

Audio
ID                                       : 2
Format                                   : PCM
Format settings                          : Big / Signed
Codec ID                                 : twos
Duration                                 : 1 min 29 s
Bit rate mode                            : Constant
Bit rate                                 : 1 536 kb/s
Channel(s)                               : 2 channels
Sampling rate                            : 48.0 kHz
Bit depth                                : 16 bits
Stream size                              : 16.4 MiB (2%)
Encoded date                             : UTC 2020-12-17 16:41:24
Tagged date                              : UTC 2020-12-17 16:41:24

As @Former user mentioned in his post, you should put your computer specs and other related information into your signature. You can also look at mine, though I have used a variety of computers, and can't remember if I updated my signature to my main editing rig of TRX40 3960x and associated hardware. I've had the AX-53 about one year less than the AX-33, which would have basically the same MediaInfo as above, and have edited the footage on Intel X99 (Haswell-E & Broadwell-E processors), AMD X399 (1st & 2nd Gen Threadripper's), nVidia GTX1080, nVidia RTX 2070, AMD RX480, and now both editing rigs I use have AMD Radeon VII. This, going back using either VEGAS Pro 15, 17, 18, & 19, along with VEGAS Movie Studio Platinum 15, 16, & 17. Depending on when it was, or which machine, the XAVC needed either Proxies at the time, or transcoded (Usually used Grass Valley HQX - put original clip(s) on timeline, then render using VP or VMS). Nowadays, its pretty easy, of course, depending on your hardware.

Hope this helps.

Hi Both and thanks for taking the time to respond....I have now updated my 'signature' to give anyone looking at my posts more idea of my setup.

So - time for a major admission...I am completely self taught and a lot of the terminology that you guys are using, in an attempt to help me, mean nothing to me.....sorry.

Let me try to break things down: I am a Steam Railway enthusiast and use my cameras to capture what I enjoy and provide any projects that I create FOC to friends within the Steam Railway community. I have been using various flavours of Vegas for the past decade, or at least it seems that way!!, to create Blu-rays and have managed to find a way to produce what I want to and am still enjoying doing so.

I have recently decided to upgrade my video cameras and have purchased a pair of Sony FDR-AX53 units as my older cameras were becoming unreliable and repair costs were becoming prohibitive.

These are the first cameras I have owned which are 4K capable and I would like to start shooting in this higher resolution and then producing, hopefully, better projects via Vegas 18.

I do not, currently, plan on connecting the cameras to my workstation - but will use the Class10 SD cards in USB3 card readers.

And so what I am really hoping the community might help me with is any settings for Vegas Pro 18 that will help me utilise the 4K captured stream from the cameras to create quality Blu-ray output.

Thanks again for your patience...

I don't think there's much special that you need to do. Try to set the camera to the framerate you want the final files to be (or x2 for special slow motion shots). Shoot at 4K resolution. Shoot h.264 (AVC) for easier editing. In Vegas let the media set the project resolution and framerate. Keep resample set to "disable resample". That's about it for project properties.

The next is render settings but that shouldn't be different than what you currently do.

+1 to RogerS's advice - that's basically what I do, though my Sony 4K camera (FDR-AX100E) doesn't have an HEVC choice.

I am very keen on railway videos including so many driver cab views in Switzerland (YoutTube lorirocks777 and Railway Emotions) and Norway (YT RailCowGirl). They were a great way to get through lockdowns.

One of the telling differences between good railway videos on YT and others - IMO - is how they are shot. There is a huge difference between YT videos shot with handheld cameras (with no stabilisation used in editing) and those shot on a tripod with a good fluid head (i.e not a tripod head designed for a stills camera). Have a look at some of the many YT videos posted by Pannier who records railway journeys around Melbourne and the state of Victoria of steam locos, early diesel B, S and T class locos and Tait wooden suburban trains restored and operated by SteamRail Victoria. Note that Pannier seems to use in addition to the main forward view camera a GoPro mounted on the tripod pointed at the 'exit' of the passing train.

@JohnJ
I would like to point out - although you certainly know this, and are used to recording at 25 frames/sec - that with the SONY FDR-AX53 you again only have 25 fps at 4k. 50p is only possible with HD, i.e. 1920x1080.  
I own the same camera, but I'm still on HD because I really like the 50p for fast movements and extracting frames from the movie.

Just simply as input.