I control around a 1000 fresh water gallons at home the big tank is a 700. Wanting to try salt and maybe get another big tank or a something like 250 to 350 gallon range and let what I put in there just go free. And I if possible I wanna put in a say 3 fish being predator stye like a jaguar grouper and some other bigger pretty that it couldn't eat. Is that possible or am I dreaming in the salt water world. I do things differently for fresh I dont follow the rules after 18yrs of it
Fish Only With Live Rock (FOWLR) is what you sound like you're planning.
My mom had a grouper and an eel in a 70 when I was growing up. That's actually my origin story into saltwater.
When I was a little older (married, kids, my own house, etc.) I was driving home and passed a thrift shop. Sitting outside was a tank that looked just like the one she used to have. I bought it for $5, got a light, HOB overflow, and a wet/dry filter and went to work!
I started with the 79, ran that for 4 or 5 years, tore it down in a move, set up a 6 gallon, set the 70 back up, upgraded to a 125, moved back to a 70 with the ESHOPPS M70, and currently running the M70, an IOAOI 8 gallon, and a 5.6 gallon homemade from a Tenecor kit.
With the FOWL, you're definitely going to want close to or more than a 100 gallon tank. 110 Extra High is a cool tank if you don't have fast swimmers, 125 or even 180 is a good tank for a longer one. My sister's ex-boyfriend had a neat 220 Cylinder tank as a centerpiece tank in his house for a while.