It sounds like his diet is fine.
When it comes to hay, whatever kind (timothy, orchard, oat hay), whatever your bunny will eat is the best kind. If you’re lucky enough to have a bunny who will eat any kind of hay, 1st cutting is going to be the highest in fiber (leafy and stalky), followed by 2nd cutting (more leaf and less stalk than 1st cutting; softer), and last is 3rd cutting (almost all leaf, very little if any stalk; super soft). In the US, timothy is normally the easiest to find and therefore the most popular. Orchard grass hay is sweeter than timothy, and can be found in 1st and 2nd cutting with the 2nd cutting usually easier to find. Orchard grass hay has less fiber than timothy, but many buns will prefer it because of the sweeter taste (especially picky buns) and may eat more so they get just as much fiber. Oat hay has alot of fiber just by the nature of the blade. My bunnies love the oat hay tops (seedheads) but won’t eat the blade/stalk. I try to give all of mine a mix — mine eat the most hay when its a mix of 2nd cutting timothy and 2nd cutting orchard. I give oat hay tops as a treat — while these are high in fiber and nutrition, they are also high in calories.