She's got a fair bit of physical strength. Probably stronger than me as I am right now. I base this on her being part youkai, Yuyuko not appearing particularly strong herself and the fact that you need a good chunk of arm strength to swing her swords effectively. Someone had to do the heavy lifting all that time when the border was strong and Youki wasn't around.
Of course compared to other Touhous she doesn't even lift but compared to normal humans like me she seems pretty strong. Not to the level you couldn't reach yourself with consistent training.
Where she does have mad hacks is in speed. If you take the name of her spellcard "200 Yojanas in One Slash" literally she can move at 1/4 the speed of light. Given that she's yet to destroy the earth I just take this to mean she's really fast. Far beyond the scope of human ability and even a lot of yokai ability just not to the point of breaking physics.
Combined together she's pretty stronk. She's a stage 5 boss/stage 6 midboss and has helped resolve several incidents so I think it's fair to say she's pretty high up on the Touhou power rankings.
Half-phantoms live really long too. Even if her growth rate slows down by a lot she's going to get more and more powerful. For this reason alone it seems likely that Youki is among the strongest in Gensokyo and eventually Youmu will find herself in the same position.
I don't think she'd know much magic. She'd focus on physical attacks.
Stronk waifu is stronk.