On the selection - and admitting a club bias is bound to play a part here.
Dan - Borthwick sees something in him, but it's not like there's a long list of clearly better hookers being ignored.
Ewels - gets a lot of grief here. He's never going to be a good international player, but I don't recall any absolute howlers from him - red cards aside (and that's a hell of an aside) I don't see who is available and ahead of him. In a side distinctly lacking experience at international level, I can see his 30 caps going a long way in his favour.
Spencer - Has failed at international level, but between him, JvP and Quirke... I'd have him ahead of Quirke on form, and ahead of JvP if this was a club game. But he's a starter or nothing. If he's in the 23, then he's in the starting XV, so if he's ahead of Quirke, then he's ahead of JvP by default.
Slade - a worse selection than Ewels, but with the same justifications. He's not going to panic at the intensity of international rugby, though with some of the howlers he has had for England I'm not sure that's saying much. I think I would actually be more nervous (but also more excited) about the idea of 2 uncapped players, than of 1 uncapped + Slade in the midfield.
Muir - he's one of a ranch of promising wingers. He's the oldest, but then he also took to 15s later in life. He's not one for 6 years time, but if he takes to it, could easily be one for 2 years time. All of the ranch of wingers in this group have their downsides, some it's handling, or positioning, defence or aerial skills; Muir's is longevity. I wouldn't say that any of OHC, Murley, Roebuck, Radwan, Muir, Eliott, PBB, Hendy, Ibitoye... He's probably got the 2 most well-rounded on the pitch.
Steward - next cab off the rank. Whilst I think we have better alternatives who also fit in better to play the same gameplan as Furbank, there's no denying that Steward is the next choice after the Wing Commander.
Tactically - Borthwick is yet to excite me, or show me that he was the right man for the job 2 years ago. Whilst he did enough in the RWC23 to get to this point, I don't think I'd be renewing his contract from here if I were the RFU. But all of that is a "I wouldn't start from here" - which isn't terribly useful.
ETA: Just having a quick look, and even with the good results in this year's 6N, he's up to 53% win ratio, sitting between Andy Robinson and Brian Ashton in the table