The Reptisun 10.0 is a T8 size fluorescent tube, while the 10.0 HO is a T5 size tube. The H0 tends to provide more powerful, farther-reaching UVB (from what I've read). But mostly the difference impacts what type of fixture you need to get for it.
The HO is a bit of a marketing gimmick. T5 is higher output than a T8 and these refer to the size of bulb and type of fixture needed. The 10.0 bulb is higher output than a 5.0 bulb and is specific to the bulb. In most cases what you're looking for is a T5 10.0 (or 12% with Arcadia labeling).
On the website the HO bulb is 22 inch but the fixture is 24 inch. Could these be bought together? Would the 22 inch fit in the fixture? or do I need a 22 inch fixture?? Could anyone provide links for the correct fixture since I am quite confused.