When I had a 90g last year, I ran either 1 Aquaclear 110 or 2, depending on the stocking. For plecos, definitely 2, because of how much waste. For overstocked africans, possibly also 2. For a smaller CA biotope (like I did a Thorichthys + swordtail setup for a while) or a community tank with tetras/angels/etc, 1 is probably fine.
For heaters, I had decent success with a single 200W in my 90g, but the 250W I upgraded to ran less often. I like the Aqueon Pros, but heaters are pretty much whatever your experience has been drives your recommending a brand. I've had good success with the Aqueon Pros and have gotten them cheap when Petco has sales, especially the free shipping plus 20% sale plus coupon, and I'll also click through from Discover or a similar site to get that cashback in addition. There are other cheap sources though.