In veg I let the bottoms dry down a bit and the top a lot, to cycle wet and dry for root growth, but in flower I try for a perfect constant 5ish as consistently thru the whole pot as possible.
Some strains require more oxygen, so go a bit drier but still as evenly moist as possible.
Your seed description should have a tell in it. Drier, moister, drought tolerant, that sort of thing.
Anything drought tolerant translates into "requires more oxygen", easy and forgiving translates into dead centre on the meter.
Requiring extra calcium and/or magnesium translates into closer to a 6 as calcium/magnesium needs water to be mobile.
So see if the seed company gave you any hints and translate that into your watering.
Never go wet tho, just a bit moister or a bit drier.
Watch the leaves, they will tell you. If they have a bit of a mottling in them after a couple hours of lights on then your soil is a touch too wet and/or cold, and the 2 usually go hand in hand as moisture cools.
Wait at least a couple hours after lights on to judge tho, as plants pig out on water over night and are often plump in the morning. They like to cool down at night.