@ONESPACE This post is written partly to address a couple of your points but also to maybe help the poster. Cheers.
I have around 200 hours in the game. I have only driven the GT3 cars 5% of the time.
My "favourites" are the Yellowbird, Group 5 monsters, Clio Cup, Formula A, Classic Lotus', Mitsubishi Evolution, Zonda R, Aston Martin DBR1/300, Radical SR8, Formula Gulf, Escorts Mark I, Caper Monterrey Stockcar (NASCAR), Mercedes CLK GT1, Caterham, BMW 1 Series M, BMW M1 Procar, BMW V12 LMR, Ford Sierra Cosworth, even the Karts are great once you get used to them. I could go on but I really do love pretty much every car in the game. You get the picture.....your post made me look at the list of cars and there wasn't a) one I haven't driven and b) one I didn't like.
For me GT6 may as well be Need For Speed now. It's been made unplayable by the generally superb handling of Project Cars. To be fair that has been coming for a while with me using the likes of Stock Car Extreme (dreadful name but great handling) on my old PC.
While there have been some bugs, they have been an annoyance only occasionally and the situation has improved hugely since launch. You learn to design the races around what you know works.
In my opinion to get the most out of it (and you do need to put time in to get the most reward) the most important things to do are.....
1 Wheel - generic ffb setup from the options menu. Do that first. A good setup varies by user and their equipment. Help on here and official site.
2 Controller settings for the same reasons as 1 (again plenty of help on here and the official site)
3 Make the gameplay option settings to your taste. There are more options in the game than any other driving game I've played.
4 Force Feed Back per car (only once 1 is done)
Once you've done all that then you can start to tune if you like to. I drive most cars with the default setup but that's only after wheel/controller setup. Tuning improves performance and something I have dabbled with a bit but get the other things how you want them first.
I use full simulation mode, with a combination of realistic driving aids (what the car has in real life) and no aids.
If no other game ever came out this would be my game until I die.
I've played many driving games over the years. Here's a selection of some of the Autosport based ones of those and where I rate them for their time. It's not every driving game I've played but gives an idea. Most have been played with a wheel at some point. I also use a controller fairly regularly although obviously prefer the wheel.
Anyway for what it's worth here's my list of how I rate other racing games.
Game Stock Car Extreme PC
Gtr2 PC
iRacing PC
RFactor PC
Geoff Crammond's Grand Prix 1-4 Amiga/PC
Forza 6 XB1
GT5/6 PS4
Forza 4 XB360
GT4 (for offline) PS2
Grid Autosport PS3
NFS Shift 2 PS3
Dirt 2/3
Grid
Grid 2
Sorry never played Toca. Somehow it passed me by as I was never aware of it until later.
Assetta Corsa and Race Room Real Experience won't run on my PC

but AC will be mine once it's out on PS4.
Having a regular core group of racers helps with online racing. Have a look at us (CRAP pCARS - mentioned earlier) or one of the other groups. You'll find plenty of help and racing in one of them.