what font and font-size would you choose?

I'd go with the standby 12 point Times New Roman.

Personally I'd choose Arial, pt 10. But that's just me. I'm certainly no expert in these things.
Point 12 seems too big & clunky-looking to me.

I like Senatorial it has a nice clean look. very minimal

As a former Technical Writer (wrote manuals for software and hardware industries), I've done and surveys on readability tests and
Times New Roman 12 point is most preferred by Administators, Managers and technical audiences.

Not that it means too much, but I've never seen Senatorial as part of any font package within MS Word. In fact, I've never seen Senatorial font.

Arial font 10-12 point, is more often used best in Tables, Procedures and captions for illustrations and figures.