TeaLeaf:
Yes that is quite true on android OS. good point. I just HATE having apps open. its the neat freak in me. i do it on all OS. i especially found on OSX, when I had 4Gb ram, i couldnt have more than 1 app open before hitting threshold. Once I upgraded to 8GB I found the actual base was around 5GB.
Im tossing up in my head whether a 6" screen can replace a 9.7" ipad or not. Then there is the galaxy s8 plus with 18.5:9 which does make good use of veritcal scrolling. id love an ipad plus 10.5 but cant justify the cost for watching netflix, youtube etc. but im not the sort to fiddle with phone in public so is a small screen phone and a base model 9.7 ipad a better choice.
iPhone X has 3GB RAM, iPhone 8 has 2GB RAM. I saw a video here that might help you with the obsession of closing apps ;)
You may be talking about desktop computers though. 4GB is a bit light for a 2018 desktop.