If you want to use t5HOs, you can go with either option - the 48" fixture or 2 24" fixtures. Either way, part of the light is going to be blocked by the center brace, but that is ok.
Higher powered LEDs are also an option. While your stock LEDs are probably less than 1W per diode, there are very good LED
solutions that will do a phenomenal job in growing plants - though they will be more costly, at least up front, than a t5ho fixture. However, the cost can even out over time since LEDs do not require bulb replacement, and t5ho bulbs must be replaced every 6-12 months or so.