First thing. You can absolutely get bonus perks from tedd trials and the spores after reaching the 4 perk limit, tested this with soda fountain and then I used peraholic and I was able to get permaperks. With soda fountain I got death perception after buying speed cola and I could see enemies through walls and repair armour quicker but the speed cola perk logo wasn't visible, but I was still getting the benefits of the perk.
Second thing. While you do need to have all the grim relics active to unlock the first sinister relic, you don't need all 3 grim relics after that, you just need to be in tier 1, so 1 grim relic and 1 sinister relic is fine, you don't need to nerf yourself completely or add dumb mimics to the match or remove your power ups. I tested this for the 6th relic with the vril sphere and the teddy bear and I was able to get the bottles from the zursa and the tedd trial and do the focusing stone trial.
Tldr; you get bonus perks and you don't need every relic active, you just need enough active to reach the tier below the relic you are looking for. You don't need to add sneaky mimic props to the map.