For the second one, why is AVC in a MP4 wrapper opening with compoundplug and not so4compound? In preferences/ file i o make sure legacy AVC is not enabled. That will let you Intel UHD iGPU do decoding which should speed things up. The reason to disable it is if there are stability issues.
The bandicut file is heavily compressed (4K file that's 24 min and only 200MB. 4K from my camera is about 700MB/minute).
You could try re-encoding it to a less compressed AVC file (or ProRes if you have a lot of diskspace) using software like https://www.shutterencoder.com/ and may find it plays back much faster in VEGAS.
If you do a benchmark we can see if your system is performing as it should.
@naren17 May not be a problem to render with normal speed unless you use an older rendertemplate . Can you give a screenshot of your used (customized?) rendertemplate?
Yes, I think ProRes is the best format as it's lightly compressed and plays back very well in VEGAS. If it's an 8-bit source, 422 should be adequate.
For rendering settings yours are fine for 720p. For final renders I also use MagixAVC with Mainconcept for better quality at the same bitrate. QSV and NVENC are way faster though are lower quality for the same bitrate (if file size matters). Experiment and see what's acceptable to you. If there are artifacts raise the maximum bitrate amount.