Nice work. Set to watch. The 260XL is a great light. An additional 135 will certainly rock the tent. You probably wont need the carbon filter until flower. I would save it for then if you can. It is only needed to remove odors, which aren’t strong until mid-flower. The exhaust fan alone is fine during veg. You got the equipment, now what are you going to grow?
The numbers HLG uses in naming their lights is what the light draws plus / minus. The 135 draws up to 150 ± and 260 draws up to 250. The XL has a wider spread than the basic 260 models. You certainly will not come up short with using both the 260XL and the 135.
I run several 260 rspecs in a 30 x 72" closet.
The XL 260 is a true 260 W light - mine actually draws 272.5, per my meter. I added an additional 135 to the center of the heat sink. It’s actual draw per my meter is 160.
Ive played with that idea for 2 years adding a 260xlv2 board i have left over from upgrade to the r boards. Just not sure if it a value to me other than efficiency.