My comparison is H264 not H265. I don't have any HEVC files. I would say V18 will be your best bet in the long term as updates will be coming while V16 is finished.
@Jacques-Brassard Curious what your general settings look like... does not appear that you are using your onboard Intel igpu for decoding. In v16 make sure "Enable QSV Encoding and Decoding (when available)" is checked. If after doing that (and restarting) you don't see decoding activity on the Intel HD630 performance chart you may also need to go into the Nvidia Control Panel and set Preferred Graphics Processor to "Integrated Graphics". However your setting in Vegas' video preference screen should stay the way you have it, set to "Nvidia". If after doing all that you still see no activity increase on the Intel task manager chart, you may have to update your Intel igpu driver to get a version that includes the OpenCL api... your motherboard vendor driver support page is the best place to start with for that. There's a free utility on TechPowerUp called GPUz that will allow you to quickly inspect your video driver api's. I think v18 includes additional Intel support which makes this less of an issue. In any event what you're after is to send all your video chores to the Nvidia except for decoding sent to the Intel igpu to split the load for the fastest renders and previews. Also keep in mind that all this depends on your timeline source clips being compatible with gpu decoding... which appears to be the case since you show decoding activity on the Nvidia board.
What a nightmare. So Obviously my setup is not right.
NVidia GTX 1070 Ti is not being utilized. Onboard GPU is not being used.
Also when it appears your GPU isn't being used have a look at the cuda window. With Davinci Resolve all the GPU processing activity is seen in 3d windows, but with vegas it can have more activy in cuda window @Jacques-Brassard
Techgagehas been really good about providing Vegas GPU & CPU results. The TOP scores are an Intel Core i9-10980XE WITH various different GPUs enabled & the bottom tests are CPU encoding ONLY.
On my 9900K with VEGA 64 LQ, I get some great render results and can render (2-3) instances of Vegas before my CPU hits 100%.... And, even with (6) instances of Vegas rendering, CPU at 100%, the GPU only gets to about 50%... Therefore, if Vegas is your primary app & you want to maximize bang for buck, you've got to pair the right CPU with the right GPU.
18 months ago, IMO, the 9900K & VEGA 64 were the best bang/buck. For the money it beat more expensive Threadripper & 2080ti combos for Vegas work....
Currently I am looking at upgrading another workstation & am considering the new AMD 5950X & Big Navi, but I need to see Vegas results first.... Hopefully Techgage will test those combos soon....