Phone 2: Wi-Fi signal weak or barely functioning, youtube videos buffer and load for much too long on 720p when they shouldn’t need to.
Are you blocking ads ?
Does that phone have apps which may be eating your resources ? f-droid.org/en/packages/eu.faircode.netguard/ With NetGuard you can block access for mobile and / or WiFi per app, or block all including system apps and then allow the ones you need.
mod_pp