IQOO and Realme has different UI. IQOO china would be on Origin OS while global rom will be on Funtouch (not sure how fun). IQOO would cater more towards gamers while Realme is a mixed bag. Personally I had good experience with IQOO Neo3 5G (china rom) that I bought from Mommar on shopee except for the lack of widewine L1 which is required for Netflix HD and some other. Also sometimes china rom has some weird problem with apps like mcdonalds causing it unable to load. China rom also has a weird bug of loading http link in SMS only via their official browser despite after setting default browser to chrome. Other than that, I actually prefer the china rom for higher FPS in games, ability to use phone nfc to copy access card for condo/office just to name a few.

I also have a GT NEO 3 MY version aka global rom. Despite having a better SoC, unable to set higher fps in games, unable to use frame plus to smoothen game fps (if fps below 60), unable to copy access card, but came with gapps baked in.

The IQOO on China rom also can install gapps including Play Store manually via their app store. They had google framework baked in but without gapps. A bit troublesome but depends on your liking. My son love it since can use higher FPS in games.