while it's a bit OCD-triggering for me to only have a single-fan video card when there is room for small dual-fans, and there's a dual-fan grill design in the acrylic cover, the single-fan RTX 2060 and 2070 from Gigabyte are an ideal fit otherwise. they require a tiny bit of finnegling to get them slotted properly, but it's not crazy difficult, and they're a perfect fit. i guess you've seen you can still use the front 2.5" hdd spot and have enough room to work with cable-management in the front area. it's also more flexible in the ITX video cards world, lol
as for the accessories, if you intend to use a flex-atx power supply, i recommend the psu cover, because it is a perfect fit on top of the flex-atx psu. if you intend to use the hdplex 400 like i did in the end, it can't be used, but in that case you'd buy the flex-atx to dc-atx psu adapter bracket to have something to fix the DC-in jack to
if you have only one case fan header on your MB and don't already have a fan splitter, their fan splitters are as good as any i guess. i already had one so i didn't need theirs. also make sure you have 2x80mm fans to use on top of the case, it helps a lot with cooling!