Retaining walls resist overturning from 1) soil expansion, 2) moisture behind wall pressing on wall, 3) a surcharge on wall, and 4) moisture freezing behind wall.
1) Clay type expansive soils is the big problem here. It sounds like your soil is not clay-ish.
2) You indicate that you’ll be installing a french drain and your soil will allow moisture to flow through to the drain, so no problem with moisture.
3) Do not park cars near the top of the wall and you won’t have trouble with a surcharge issue.
4) Freezing can be an issue, but a french drain will remove most of the water, so I wouldn’t anticipate a problem with freezing.
It sounds like your retaining wall is a “gravity retaining wall” rather than a “reinforced retaining wall”. That is to say, the weight of the wall material will keep it from overturning, which is fine up to about 1m or so. Higher than that, and it should be reinforced.
I’d lay the bricks flat (not on edge) and if you mortar them together, make sure the french drain is at or near the base of the wall.