yeah a flat bed is definitely rthe better option.
The problem with the sapphire plus - is that it has 2 z-axis motors.
So keeping the bed flat without any lateral slant is going to be difficult.
In that case an 'auto levelling' system will actually help level a slanted bed.
And given that even a few hundredths of a mm slant will make a difference - it's probably worth using the bl touch.

getting a print bed lined up properly on a dual z-axis printer is always going to be bloody difficult.
That's the main reason, that if you don't need the extra build volume - the sapphire pro2 is the machine to go for over the sapphire plus.

Although how accurate those bl-touch clones are - who knows ;-)