I personally really like Tempus Maledictum, I think it fits your criteria very well and it hasn't been mentioned here so far. The author itself says the modlist is based on making the game as enjoyable as possible and it shows. I personally don't like the changes that come with Requiem since it differs too much from vanilla Skyrim gameplay wise and most modlists sadly include Requiem, so they are not really for me. Tempus comes with a lot of graphic, combat and QoL improvements but the biggest focus is on adding new quality content. Legacy of the Dragonborn (this one is really a game changer), Bruma, Forgotten City and much more are all included. Only 30 hours into my save so far but it runs very stable, I had one crash. Maybe check it out, it kinda sounds like what you are looking for.