-It might break, no guarantee that the project will work if you download a new version and open your project with it. Once a project is converted to the new version you can’t go back so keep a copy of the project at the old version just in case.
-The only really usable solution is VXGI, UE4 has another method called LPV but the quality is very poor and the performance isn’t very good either and you can’t turn up the quality as high as VXGI.
-They use similar methods, but from what I gather VXGI is a bit faster. The reason SVOGI wasn’t included was because they were using GTX680 graphics cards for it to work, which most people don’t have something like that. Also, it doesn’t work on game consoles (PS4/Xbox One) which all means that if they wanted to keep the feature in the engine then it would only benefit a small group of people–basically PC gamers with high-end graphics cards.
VXGI is developed by Nvidia, and it’s not fast enough either, but Nvidia made it available anyway. I don’t know of any games that use VXGI.
-It’s already doing what it can, I mentioned before some things that can be done to improve quality–higher quality assets and the few settings that you can turn up.
-People don’t turn up the graphical features as high as they can, but once you do there are limits to the quality available. For example, you can’t increase the resolution of reflection probes, and anti-aliasing quality only goes so far. I think even GPU particles are limited to 1,000,000