I have two pairs of Truman boots and I quite like them, in their Java waxed Flesh and Black Oil Roughout. Boots are of good quality, stitching has no issues and I can't find any real defects on either of my pairs. All in all I'd say you're good to go construction-wise if you like the look of the boots. Personally, I brannock at a 10.5D with an average instep, and I find going true to your brannock size to be the ideal move. Half size down for their 79 last, which Truman recommends, was way too small for me.
I second this.
I also have to pairs in the 79 last (Java waxed flesh and shrunken bison). Quality is good for the price. You will find criticism on their QC, but that’s always, “heard it from a friend”.
Sizing is maybe half a size more generous than RW Iron Ranger/Blacksmith. I picked the same size, and it works for me.