I'd say there are more 17x7.5 wheels that fit GS specs than 17x9 or 18x9 wheels right around the et45 that'll work well for STH,Most of those tires above are ones I’ve looked at. I like the Firehawks but would want to run them on aftermarket wheels keeping my OE setup for winter. It may be easier just to run STH because there are very few appealing aftermarket wheels that are only 7.5” wide. I’ve actually never had a true summer tire, on my Jetta I ran Proxes 4, Kumho Ecstas and DWS and honestly rarely had complaints. I also wasn’t doing anything competitive and the 2.5 was underpowered.
Lightweight 17x7.5 wheels for GS off the top of my head, roughly from cheapest to most expensive:
Sparco Assetto Gara
200tw tires are more fun, period. You can usually find a used but not too old set from a regular autocrosser for a good deal, too.
If you have an S and get serious about autocross and find that the lack of a PP/VAQ diff is holding you back, you'd want to get a Wavetrac LSD and move up to STH. If you have a DSG, be aware that DSG tuning is not legal, however.
On a related note - I ran a couple of events in STH with my GS-prepped 2017 GTI Sport DSG, but with a Cobb AP and MAP stage 1 tune, and found that the extra power really wasn't that useful. I feel that I needed more mechanical grip (stiffer suspension and wider wheels/tires) to really go any faster than my usual competitors in GS. However in a straight line and on the street the car was FAST!