My thoughts on your options:
X3M40/X3M - With the minivan the only practicality you need are access for golf clubs, which I would imagine the sedans could easily handle, if not bring them to the test drive and see whether they fit in and out of the vehicle. X3M in my opinion is too stiff of a vehicle, however you may like that as you said. Ventilated seats in BMW's are pretty weak so even if optioned it may not provide many benefits and the ventilated seats in the 40i are very hard/uncomfortable. Decent handling, good engine, numb steering, but not as fun as a sedan, and the interior is outdated and feels too cheap in my opinion.
M340/M3 - Great cars, however the M3 hasn't been released so can't speak about that. Coming from a 15 year old C320, I would imagine that you don't need a full M as an M340 should be more than enough power and still have good handling and be practical enough, and new M3 is gonna be hideous so that would rule it out for me. Personally I find the steering while not a deal-breaker, very disappointing and the handling while great, is not class-leading or much better than other competitors to make it the "go-to choice," like it use to be in the old days of the E36/46/90. Still a great car, but the competition has caught up and is worthy of a look.
AMG C-Class (43/63) - Great cars, both the V6 and V8 are very nice. The ride is stiff but of course again you'll have to be the judge of that. The V8 in the C63 is pure bliss and something no other competitor but Cadillac will offer in this class of car, and will likely be the last V8 C-Class so it could hold its value more in the future. The V6 in the 43 is a pretty reliable engine too and feels very aggressive and wants you to drive like a hooligan which is pretty fun. The new C-class also handles very well, and has a better exhaust than both the M340/M3 in both V6 and V8 form, and just has a bit more drama, in a good way though. Steering while not brimming with feel, is more natural in the corners with an overall less synthetic feel than BMW's. The interior is also much nicer in materials and just makes the cabin feel more expensive of a car in my opinion. This would be a nice upgrade from your old C-Class, I'd recommend test driving both 43 and 63, while even the 63 probably has more power than you need, its hard not to like a V8 (which will soon be hard to find).
AMG GLA - Not a fan of the GLA, one of the worst MB's in my opinion, however I have not driven the new generation which looks to have improved upon the old, either way, I'd stick to a RWD bias car like the C/GLC over the FWD based GLA, especially if looking at AMG.
AMG GLC (43/63) - Copy and paste everything from the C43/63 and add air suspension for a better ride and of course greater practicality and new technology (MBUX). My wife has the GLC 300 and she really enjoys it for daily driving. She test drove the 43 (and I've driven the 63) but didn't need that much power since we also have a Z4 M for fun. Again though, I think the C-Class should be practical enough for your needs.
Genesis G70/Kia Stinger - I know you didn't mention Stinger but its worth a look. You get a mix of SUV practicality with the hatchback so golf clubs should be super easy, and you get a bigger backseat than the G70 as well as more "unique" styling. Both cars handle well with the edge going to the G70 since its smaller, and are getting a nice mid-cycle refresh with an upgraded 3.5TT V6. These could be the best cars for long-term ownership as Hyundai reliability has been very good over the years, and the value is very good as well as the warranty. Only downside is really the dealerships are not as nice as the Germans. Kia/Hyundai also have much better ventilated seats (which I believe are actually AC cooled, not ventilated) than the Germans.
RS5 - Overall not bad, but very expensive and not a fan of the transverse FWD based platform Audi uses. Easily the most comfortable car here but not the most fun, and the RS cars are hard to find with good deals.
Model Y - Get a Model 3, better build quality (although still not great) in the 3 vs Y, and better looks (again still not great though) and more than practical enough. They drive well and have good range but its a very different experience than a gas car so only you can really decide if its the right move. 10-year ownership costs/reliability is also a question mark.
Mach E GT - Not coming out for a while, but a very nice car from the looks, but not much is known on how it drives, handles, and reliability since its not out yet.
Polestar 2 - Has all the great Volvo qualities, but I'm betting it will also handle like one (aka not fun) and also incredibly expensive. Same with the Mach E and Tesla, 10-year ownership/reliability is a question mark, and the car is not out yet to test drive. Range will also likely be very low for the Polestar.
Overall, I'd suggest test driving (and make sure to bring the golf clubs to test out practicality), the M340i, M3 (if its out), C43 and C63, as well as maybe a Kia Stinger or Genesis G70. I don't think you should go the SUV route unless the golf club situation doesn't work out.
Edit: Add to the list (if your budget allows it) a Macan S/GTS. The best driving SUV in the segment if you are forced to go into SUV territory. Feels like a hot hatch on stilts, and can easily fit golf clubs in the back, and the interior is a very nice place to spend time in.
Good luck
