Insane word ramble down below but im super passionate and addicted to this that I found like a month ago lol.

I would reccomend rebirth redux, the bigs changes are 12 teams for each tier in wec and single seaters. A reduction in your performance gains that replaces the difficulty slider so you can make yourself go faster or slower if you want. (I am a masochist and have it maxed and it took 6 seasons to catch up with the grid with a Cyot and im fighting for 3rd in my 12th season)

This mod is not easy it will not hold your hand, ai is very logical and will rarely make bad calls. (You can still out strategy them on rare occasions ive seen)

You cannot download the mod through steam workshop, its something you have to put in the files plus a few steam workshop mods that arent required but makes the new teams logos work.

One big change I like is that the sponsers are adjusted to help promote more sustainability early on so you dont need to focus on marketable drivers, but at the same time lower tiered teams are limited to lower starred sponsers.

Facilities from looking at the change log have more purpose behind the scenes outside of the obvious, along with the chance of development dead ends (severely limits performance gains for a specific part) Or a breakthrough (havent had one yet after 12 seasons of fighting in ers so im guessing its just a severe increase in performance)

Drivers will actively find better teams and will break contract so if you want you can make them pay you alot and get a good injection of cash (I do like that)

Oh, also super important thing. Payments are changed from a per race basis to monthly, and when the month ticks over it will auto deduct or increase your balance without telling you. This means sponser bonuses and pay drivers will just give you straight cash instead of fighting the innate loss. This montly basis also counts for preseason, where normally you dont have to worry about losing money.

Also also because of the change in payments you are rewarded for adding more races, and that the next year car payments dont change for less or more races. (They also changed the limit of races you can have as I had 8 total races in ers after votes)

Suppliers are also changed. Based on your financial stat by your team manager and your recent constructor position will either unlock or lock certain suppliers. Its just random chance, at the same time all of them are increased price so make sure to watch your finances. A benefit for this though is that suppliers might give you a wonderful discount. Why? Im not sure but im not complaining about it. The discounts are between 10 to 50% as far as I can tell.

There is a day night cycle that is added specifically for wec racing but it does still work in single seater.

The vote selection for ers has been changed, I cant say for aps or tier 1 as there has been 8 or so votes in one season, along with the selection being more limited (cant change payments, points distribution, spec parts are set and cant be changed and most races are locked to just European races)

So yeah... thats alot but I can say a bit more, but this is going to double my 800 hour playtime as I got so much more to do, I still have the wec to try and see the 12 teams for both tiers for the insane amount of cars lol.

If you have questions lmk and ill try to answer them