Mixing with midi

What is the correct way to mix with midi? I'm quite new to recording with midi. I still don't even have my gear setup properly yet. But I'm wondering how one goes about mixing takes down to a final master? Let's say you have two audio tracks and five midi tracks. The five midi tracks are using two synths (one hardware and one software). So how do you mix to a final master? Do you record the midi to audio tracks in Reaper before you mix? At what point do you take your midi synth tracks and turn them into audio? TIA

I say render the midi parts as audio as soon as the writing, performance, and sound or patch is final. Just like when you would record guitar or drums. At that point, you have written the material, decided on the sound you want, and when you record it you're going to keep the performances that sound good. With midi, you've "recorded" the performance first, and are free to change the sound or the writing / performance later. So as soon it's all as final as it's going to get, render it. No point in holding onto it. So render it and it becomes another track to be mixed like the others.

You can render the midi tracks or just use the midi tracks as they are. The midi tracks put out an audio signal just the same as an audio track and you can use the track faders and everything the same way that you do with tracks that contain wave files. There is no real need to treat them differently at the mix stage.