Hello Everybody !
Let's talk here about your Ridiculous ( Or hardcoe if you wish ) Role-Playing rules.
Let me begin..

1. Maximum inventory realism.
I often do "inventory checks" , I see if everything that I take on me is realistically placed.
For example , I do not carry potions unless there's a place for me to carry them.
Another example , I get to a ruin and there are tons of loot just thrown around the place , well that's fine but I don't have the place to carry all of that , unless I imagine a bag of loot or something ( that's how I carry books on me ).
A workaround is getting a horse , or getting the Black Market from Dragonborn DLC.

2. Were-Creature transformation.
When I transform into a Were-Creature , I imagine that all of my inventory is thrown away at the place of the transformation , and obviously after that I "have to go take it back".

Well probably there are many more rules , I'll add later.

Far too strange for me

Walk,don't run unless in battle.

And these are just the basics.

I don't really have any rules, but I do what I feel like my character would do... The outcome is about the same anyway.

Such as, my character would want something warm to wear in the colder areas of Skyrim, so I keep a hood and a fur cloak (from mod) in my inventory, and I also keep warm clothes for my followers to wear. Unless I have bags and satchels on my cuirass, I craft a backpack (mod) because it does feel strange to carry all that stuff around but not having anywhere to put it.

I usually take off my clothes if I go for a swim, I don't eat venison or the like for breakfast, I usually take off my shoes before going to bed... Things like that. But it's not rules, I just feel it's the natural thing to do.

Going behind cover to drink a potion or apply a poison in battle is something I'm doing more often. Wouldn't say it's a rule, but I'm less than happy when I pause the game just as a dragon's about to douse me in flames, so I can drink a potion of resist fire.