If you want 'power' you won't find it on most tablets, even Samsung's. BUT when tablets are concerned, you won't find better specs than Samsung's Tab S series (at least on the Android side of things). If you want decent performance though, stay away from the A series. That's a mid-to-entry level tablet.
Also, I'd wait at least until the Note 10 is announced. Rumors are that the Tab S5 (or also rumored to skip the number and go straight to 6) will also be announced there and released by August. Worst case scenario if you don't like that one, the Tab S4 will come down in price once the newer model is out.
If you can live without the S-Pen, the S5e is a very solid choice. But for non-pen users, at current bargain prices (especially for Prime Day) and while I LOVE my Tab S4 and using DeX on it, it's hard to recommend an Android tablet over an iPad.