Back spacing and offset are different things I believe. Back spacing is the distance from the plane of the wheel where it bolts to the axle to the inner rim edge. Less back spacing actually places the wheel farther out from the axle. Most front wheel drive and later 4WD trucks use wheels with a lot of back spacing, placing the majority of the wheel inboard of the lug nuts. Many of the oder vehicles used less back spacing. High back spacing can lead to rim/caliper interference issues, so this is something that you should get right.
I don't remember at the moment what offset refers to but I think it is a reference to the difference between the centerline of the wheel and the plane of the mounting surface.
Aluminum is lighter than steel of the same bulk, but as wheels go, these aluminum wheels (TX-1) are probably on a par with standard steel wheels as far as weight goes. Or, they may be a bit lighter. I would not call these featherweight wheels as they are quite dense, a good thing if you are looking for strong wheels. They have a far higher load rating than a standard wheel of either aluminum or steel, rated at 1,400 kilos per wheel. That's about 3,080 pounds per wheel, which is on a par with most forged aluminum wheels (The TX-1 is cast, not forged -- the website has a typo in that regard), and those using tapered lugs, as most of ours will, have steel inserts at the lug nuts. Quite a few aluminum wheels in this country have no inserts, which is okay for general highway use, but which can cause nuts to loosen on the trail or under hard use. The inserts help to prevent this.
VTO Performance also has lots of other brands and styles which will fit most vehicles, including some of the harder to fit trucks. If the TX-1 is not what you are looking for, I would not give up. Contact Terry at VTO and ask what he can get for you. I found him to be extremely accommodating and willing to take the time to answer questions.