Building up my first s/s with simple horizontal dropouts (used sliding dropouts or eccentric bb before) – will a normal QR skewer hold the rear wheel securely without pulling to one side – or should I use a bolt up hub?

Ta

Should do. Bolted up hubs are better though. Be aware that if you’re running a disc brake, that will probably pull the QR, rather than any effort you put through the chain.

I would heavily advise you either use a bolt-on rear hub, or use a chain tug for at least the drive side. I tried this setup once and I didn’t get far from my driveway before the torque of the chain overcame the q/r skewer. Last thing you want to do is power along a trail then have your rear wheel suddenly stop because the tyre’s jammed against the frame….

Personally, I would use a tug all the the time on an SS. Even with bolted hubs I find the wheel pulls forwards.

I use chaintug (drive side only) and XT qr on my On-one and it has never moved.