I'm sure this has been asked (Sorry, not sorry)... I searched but could not find the thread. This could go in General or in Publishing. I have not one, but two questions (a 2-fer)... 1. Font style (assuming 12pt) you prefer to write in? 2. Font you submit your MS in for TP (assuming the publisher has their own guidelines, but in general)? I want to see how it makes a difference, visually.
I write in 10pt Verdana, single-spaced. I've previously used Times New Roman, Arial, Calibri, and Candara. When I'm getting things ready for submission I default to the Shunn manuscript format, which is 12pt, double-spaced, and TNR or Courier - I prefer Courier, but yeah, if the guidelines prefer TNR I change it. I also usually adjust my margins, because I don't think libreoffice's defaults are quite wide enough. With all that you end up with a lot fewer words on each page, a lot more white space. It's a pretty different feel.
I like writing in double spaced Courier just because I find it easier to read and edit and gives me lots of room to pencil in changes on a hard copy. I submit in whatever format the submission guidelines say, which is now usually Times, but when I first started Courier was more popular. Back before digital manuscripts were a big thing, though, occasionally I'd be asked to give the Editor a copy in Times, or whatever they preferred, and another copy in Courier for the Typesetter.
I'm same as The Dapper Hooligan. Courier, double spaced. Usually 10point, but point size depends on the screen. I bump it up to 16point on my laptop, because the pixel density is very high, I'm 49 years old, and 10point is unreadable for me on that gadget. My arms are too short. ETA: I like Courier so much from a design perspective, that style=monospace is the default font on my website.