Shorter Centre backs are rare, but there have been a few over the years, from Moore, Koeman, Puyol, Beresi, Cannavaro.... a brain and positional sense can be as useful as height.
Isn't Scott Wharton also only 5 ft 11?
Birmancevic is a right footer who plays on the left, and Markanday is a left footer who plays from the right, Dolan would likely compete with Birmancevic, and Hedges with Markanday
He is probably on more than our entire squad combined
Estimated £150K a week https://salarysport.com/football/player/luke-shaw/
Pretty sure that's around 10 times our highest earner
Bagan played left back/left wing back for Cardiff whenever he was fit
https://www.transfermarkt.co.uk/joel-bagan/leistungsdatendetails/spieler/742163/wettbewerb/GB2/saison/2021
Giles filled in at LWB when Bagan was injured, but Giles is much more a winger than a wing back/full back, which is only emphasised by how badly Cardiff's defence performed during that period,
Although as you state, most of his assists for Cardiff were from set pieces, so maybe he was nothing more than a set piece specialist who doesn't offer much from open play... quite why he couldn't provide a few assists from set pieces for Rovers is a mystery though eh?
Giles played as an old fashioned left winger (rather than the current fashion of playing inverted wingers) for Cardiff, according to transfermarkt, he played 17 out of 21 matches for Cardiff as a left winger
https://www.transfermarkt.co.uk/ryan-giles/leistungsdatendetails/spieler/504581/plus/0?saison=2021&verein=603&liga=&wettbewerb=&pos=&trainer_id=
The video stream graphic has been wrong almost every time I have watched it, lol
My guess is Mowbray will try and Match WBAs formation and go with 3 at the back, meaning Buckley as a wing back and Rothwell pushed forward alongside Gally and Diaz in a 3-4-3, or alternatively 3-5-2 and try and pack the midfield