You have definitely been reading, it shows, great start.
As to your lighting question leave the bloom switch off, download a LUX app on your phone and take readings at your plants canopy. Your going to want 3500 lux while in veg mode (so for the first 4 weeks roughly but we will be watching your progress, search online for a LUX to pffd converter that shows the difference light choice the one I uses sells lights so I can’t link it)
Fimming is a great idea, it spreads your canopy out, that being said you have 5 plants in a 4x4 thats normally filled with 4 and you only have 2 lights so I woild say don’t FIM.
Back to k if hting your going to want more lighting come flower for that amount of plants.
Your 900w greengo is actually 190w 1.8A
The vivosun 600w is 270w, will cover a 1x1 area at 580 PPFD come flower. So basically one plant…
Start saving $ for lighting!!! In 4 weeks your gonna need new lights!
Put your temp/humidity sensor at canopy light, hang it with some string, adjust this throughout the grow to get accurate readings.
Your going to want to have your clip fan, hopefully you have more than the 1 see in the picture to save cash go to a second hand store and buy a tower fan or two that’s use or get them off FB, you want fans to give a light breeze so they get strong and build roots.
Good soil mix, did you add 30% perlite or Mykos? If not no sweat but make a note to do this next time.
Yes you will want a easy way to collect run off, at least you have some space @merlin44 has nice ones as do many other people, the idea is to rain the plants up just enough with a platform that drains through and yet you can slide a pan or dish in and our easily without having to move the platform some do wood and metal grates, some do pvc get creative.
Make an individual one for each plant it will be idea.
But first make some domes for those plants!
Easy quick way is cut the 2L pop bottles, but look for something tall and wide like a cake cover or a 4L clear jug or something. This will keep their humidity up.
Print the VPD chart and tape it to your outer tent wall as a reference it’s a very important factor, a inkbird duel humidity/temperature controller is an ideal purchase to help control your environment I wish I got one a year ago. Go google this asap.