No, I have not tried that one but have a buddy who used to run it when he had a 2T. I tried some Amsoil once, but it was because I ran out of Yamalube in my old TS. In that thing, I don't think it really mattered what I ran. Actually, in the old TS I was using Polaris sled oil since I had some kicking around. When I took the top end apart, it was very nicely oiled everywhere and in great shape.
I have another friend with a KTM 300 (the one in the pic) and he just did the top end on that one. He is running H1R and it was very impressive the coating of oil everywhere.
For sure ride it on the street. Of course there will be some quirks and quarks for vibes and such, but if you don't care, then just ride it and have fun. I keep the gearing the same on the back sprocket (41) and just switch out my front (13 and 14). But if you have spare rims, then for sure throw a small sprocket on the rear and go to town. I wish I had some extra rims for my bike, I would keep some supermoto's and another set for my ice tires. Just makes swaps that much easier. For me, swapping the front sprocket is easy peasy and I can gear it the way I like. From what my buddy says about his 300, the only real "issue" is the front wheel vibes with the rim lock. Mine does not have one and is silky smooth, but he has taken his 300 on 700 km dualsport trips before with no issues, and that is even with 14/52 gearing. He could still have no problems keeping up with the 650's and 950's. With my 14/41 gearing I can outpull and pull away from a KLR 650 that has the 685 kit in it and cammed to heck.
Dualsport it and have fun!!!
TS 250 KSM