If your Rav4 has the 3rd row seat, it has a somewhat stiffer suspension in the rear... which will help. If it doesn't, expect a whole lot of rear sag if you get close to the 350 lb hitch weight limit.
Hitch weight is the kicker. Keep in mind that a trailer's listed dry hitch weight will not be the hitch weight you end up with when ready to camp. Figure that your LP, battery, water and gear is likely to add 50-100 lbs to the published figure (depending partly on where the fresh water tank is located).
The best small trailer I know of in terms of light hitch weight is the Scamp 16. It's so balanced, it's very easy to have a real world hitch weight under 250 lbs.
The Camplite appeals to me, too. But for your tug, the 11FK is probably the only one light enough on the hitch (225 lbs dry). Wind resistance will be much greater than a rounded Scamp, Casita or Lil Snoozy; you'd probably get 14-15 mpg with the latter, but more like 12 with the Camplite. It isn't the front end shape so much as the rounding of the edges and the narrower, lower profile of the molded fiberglass units, that reduces wind resistance and allows greater MPGs.
I have towed for about 140,000 miles with my '08 Highlander, which has the same 3.5L V6 as I think you have. I've towed several different trailer types... Burro (14 mpg), Lil Hauley (cargo version of Snoozy, 14 mpg), KZ Spree Escape (11-12 mpg), Aliner (15-17 mpg). Plenty of power to tow any of them, except on long uphill grades at high elevations, and even then it's just a matter of slowing and gearing down.
Mike G.
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photo: Yosemite Valley view from Taft Point