There is an interesting article on The reference handle cap at www.reddit.com/r/skyrimmods/comments/ag4wm7/psa_the_reference_handle_cap_or_diagnosing_one_of/ This is especially interesting given the larger load orders SSE users can now develop using ESLs and ESL flaged ESPs (pseudo ESLs). I got interested in this while working with the author of Anna NPCs on a version of her main mod that would affect the reference can to a smaller degree. I am not sure it was worth the work since as you will see from the numbers below of the worst offenders in my load order that AnnaNPCs.esp is a light weight.
1211 total in [0C] AnnaNPCs.esp. 11877 total in [C5] Destructible Skyrim.esp. 12555 total in [9B] Lucien.esp. 13827 total in  SkyrimSewers.esp. 15581 total in  CollegeOfWinterholdImmersive.esp 15874 total in [8C] You Hunger.esp. 19284 total in  JKs Skyrim.esp. 21953 total in [7B] Helgen Reborn.esp. 43382 total in [6C] Dwarfsphere.esp. 47846 total in  3DNPC.esp. 66667 total in [AF] EnhancedLightsandFX.esp. This is not the end all comparison, because item which over write a ESM reference is still treated like an ESM reference. So for example "You Hunger" doesn't use up as much as one would expect from the numbers, because it mainly replaces ESM references.
Good reminder, naramoore. I was worried about that cap when my mod count started ballooning. Happy to say I'm still less than half way towards the dangerous territory of 900k reference count: Found 305945 temporary and 98281 persistent loaded references, for a grand total of 404226 loaded references. [04:50] Done: Applying script "count_loaded_refs_in_load_order", Elapsed Time: 04:50 The non-master mods I have that load the most references are: (19270 total) loaded references in  WARZONES - SSE - DLC - Assault Attack.esp. (47885 total) loaded references in [1D] 3DNPC.esp. (34590 total) loaded references in  Enhanced Solitude SSE.esp.