Solaris is a 29er.
Bfe is a chromoly steel 26 trail hardtail. Slackish geometry, loads of standover , massively strong and capable of huge abuse.A true hooligan hardtail, from the outset capable of taking a 150mm fork.
Soul was originally a 26, but now 650b. Mk one was rated up to 130mm fork, but in later guises up to 140mm. Built using reynolds 853 tubing in the main triangle it has identical geometry to the BFe, but is considerably lighter. Despite the lower weight it is capable of just ss much abuse as the BFe, but costs half as much again frame only.
Cornered the market, or true trendsetters. I have a mk3 Soul 26, and cannot ever envisage selling it.