I need some help setting up my home network/extenders in the best configuration.  

I just purchased a BE550 Wifi 7 router which is replacing my old Archer C5 router.  In my old set up, I had an RE315 set up outside for the deck area and another RE315 down in the shed to coverer the smart home devices down there.  They were set up as just extended networks. The new router allows for onemesh which I am excited for.  My question is, would i be better off using the RE315's as access points hard wired to the modem, or should I set them up as Onemesh.  I really liek the idea of one wifi name and automatically switching to the storngest signal and not having to log in to an extended network.  The signal is weak at both the RE315's due to the distance and obstructions.  I can wire ethernet to the RE315 on the deck but not the shed.  Both extenders worked for what I needed them for as extenders on the old C5 router with the same weak signal.  

What are my best options for setting this up?  Im a complete newbie to networking.