I do a lot of work with tube bending at the company I work for.
For bending aimed towards FRC there are a few benders I can recommend, sourced from
JD^2 and
ProTools.
Within JD^2's catalog, their Model 3 manual bender (their bestselling product) is decently effective and is a machine I have worked extensively with on precision bends. It does have some shortcomings. One of the caveats of tube bending is that to achieve a certain bend angle it's necessary to overbend by a precise amount to accommodate for spring back - this will vary based on alloy and profile dimensions for the tube you're bending. Additionally, in manual draw benders, there is a small element of friction which can skew what is interpreted as the final bend angle post-springback. This requires a little finesse and testing to massage out of your bends.
An excellent way to calculate and deal with springback and overall design for tube bending is using
Bend-Tech software. I've only used Bend-Tech's EZ3D package which is limited, but the advantage of Bend-Tech is that it provides an unfolded model with LRA (Length/Rotation/Angle) data. Upgrading to Bend-Tech Pro allows for assembly design and notch calculation. Essentially it will provide you with specific instructions for the operator in order to produce the desired part. You design to CLR (Center Line Radius), but it does give flexibility as to designing to the apex (projected intersection) of the bends or bend tangents.
As to precision with this class of benders, I can comfortably say you should be able to achieve, with the raw bend, within +/- 1.5 degrees of the desired angle. From that point, it's trivia to manipulate the already-bent part into the desired precise angle. Distances between bends, assuming marks are clean and a precise point on the bender is used as reference, can be close to perfect. Eliminating cutoff takes some prototyping time, but Bend-Tech does feature a machine calibration feature that theoretically will calculate your bend offset automatically (though in my experience, it's far better to add 0.5" cutoff and create a clean cut post-bend).