That's a hell lot of phones you used buddy!
Btw, what made you buy S8+ after OP5?
Lock apps is a good option as the basic tw settings don't allow lots of apps to be in RAM. That's why the idle battery life is the best on S series.
LOL, only 2 phones. In the last 6 - 12 months I have bought -
1. Axon 7 - 6gb ram 128gb rom - great phone but took too long to unlock and I got bored with it.
2. ASUS Zenfone 3 Deluxe - 6gb ram 256gb rom - brilliant hardware, stock rom OK but a few bugs - unfortunately ASUS didn't release unlock tool until too late killing off developement.
3. Nokia 6 - 4gb ram 64gb rom - OK for a budget phone but again no bootloader unlock.... Bored now, NEXT...
4. One+5 - 8gb ram 128gb rom - really like it but running out of storage- at least the others I can put in an sd card...
5. Samsung Galaxy S8+ -4gb ram 64gb rom - got a bit cheaper so was in, still exploring stock rom so not rooted yet.
6. Samsung Galaxy Note 8 - 6gb ram 64gb rom - on pre-order... Awaiting judgement. Unfortunately living here in Oz it looks like I won't be getting my shiny new toy until mid October... Got grey import (love the description that it's Oz stock but then these things tend to come with an overseas plug with a cheap sh!tty plug adaptor) but it was approx. $300Aud cheaper than the ones avalable in shops here...
Also waiting for my Jellyphone pro, a really small android phone I got on Indigogo... So sue me, I'm a sucker for computers and phones....
Out of all these phones the Galaxy S8+ is pretty laggy in comparison, even the Nokia 6 is pretty decent in comparison. Hopefully the Note 8 is a bit faster and the extra RAM will push it back onto the top of the heap...