As it currently stands with Watson on the roster they are $21,008,826 over the cap.
His cap hit for 21 is $15,940,000 , that includes his salary of $10,540,000 and the prorated signing bonus money of $5,400,000.
There's $21,600,000 in dead money if you trade him pre June 1 which is an additional $5,660,000 more than his cap hit this year.
They'd be $26,668,826 Over the cap after trading Watson prior to June 1.
Post June 1 trade costs you $5,400,000 against the 2021 cap and the remaining $16,200,000 against the 2022 cap.
They'd be $10,468,826 over the cap after trading Watson After June 1 but would have the $16,200,000 against the 2022 cap.
I don't think anyone would want that figure against the 22 cap .... but it would be very difficult to clear enough space to make it a pre June 1 trade , being forced to clear that $26,668,826 plus whatever it took to fill out the roster.
At that $26,668,826 figure , you could cut / trade Watt and McKinney and still be $2,168,826 Over the cap , having to make further cuts to fill out the roster. Add Martin to the list of cuts and you have created a grand total of $4,081,174 in cap space.
Funny fact - The Texans spent the 6th most on player salary for the 2020 season at $211,553,068 ..... That's $52,888,267 per win.