With VP 21.300 through 23 the iGPU isn't as useful as it used to be assuming you also have a dedicated GPU. The only exception is if you use 10-bit 422 HEVC media an Intel iGPU can decode that with QSV whereas no dedicated video card can in VEGAS (yet; NVIDIA 50XX support is eventually coming).
On a practical level, the lack of an iGPU - as I found out after getting my i9...KF CPU - is that if the GPU fails there is no alternative connection on the computer to the monitor until such time as the GPU is replaced. While this has thankfully not happened with my current computer, I have had GPUs fail a couple of times years ago on previous computers but I could continue on by uninstalling the failed GPU and connect the monitor to the computer's iGPU plug.
Since vp21b300 I've been getting better Vegas performance disabling the igpu windows driver or in bios. Not having it at all might give the other cpu modules more elbow room for better cooling... assuming the igpu chiplet is actually absent and not just disabled.
For relative GPU performance you can see two benchmarks in my signature. I wish we had some data for the newer Intel GPUs.
@RogerS Charted Sample Project time for the Asus Nuc that I got in just in time for when I hit the road next week. Ultra9 275hx cpu, 32gb ram, 5080 gpu: 43.75s 4k nvenc render with vp23 b356. Only thing not stock is that I moved the boot drive which came in on a pcie4 m.2 to the pcie4 slot and installed a 4tb pcie5 m.2 as my D: work drive which I ran it from and rendered to. Also ran it on 11900k/64gb/5080: 59s.
There's also an igpu on board identified only as Intel Graphics and an NPU but I'm not referencing them anywhere explicitly in Vegas, although I see an option to render QSV which I'll probably use to get around the gop/nvec problem in vp23.
Moving to VP23 should improve your playback, video editing workflow, especially for difficult media. (you are currently using VEGAS Pro Version 20.0 Build 370). Consider it when the next build after 302 is released.
The playback for difficult media changed up a gear with VP22 and VP23. This may not be only due to GPU optimisation but maybe better CPU threading.
Obviously changing up the GPU is easier than a new CPU and all that it entails.
I'm specifically thinking of some Sony hevc media that uses all B frames, no P frames, produced by A7S III, A7R V, A7 V etc, I have test samples. There is a sample supplied by @AVsupport previously from his A7S III that can be best used for this type of playback testing.
You could perhaps test the next VP23 build on release to see if it's worth it.