You shouldn't need to convert H.264 (AVC) to ProRes for use in Vegas Pro 22. Pre VP22, even less so if your GoPro video is HD rather than UHD. I found that GoPro HEVC (H.265) video needed to be transcoded to another format because back then, VP had problems with H.265 video, but developments in VP22's video engine now avoids the need for H.265 video to first be transcoded.

Re ProRes, you might want to do a test transcoding to ProRes and then likely realise that the size of ProRes is enormous compared to the GoPro original video size. If there are only a few short GoPro shots, that may not be an issue, but if your projects are large and substantially use GoPro video, then your computer is going to need a large amount of free storage, preferably internal storage because data transfer speeds between external storage are slower than occurs with internal storage especially if the connection is just USB2 or 3 - USB-C to USB-C would be better though.

BTW, when mentioning your computer specifications, please include the generation (e.g. i7 13xxx...). Please look at my Signature below this comment and perhaps add in your forum My Profile under Signature the full specifications for your computer and related equipment.