Need to know what you're making for PSI first.
Pros and Cons to everything- We run the Merc Racing relief valves plumbed after the coolers before the t stat or crossover. Strainer mounted (or anything before the raw pump) ones can suck air if they stick open on first start, fast track to a burnt impeller. On the raceboat we used to cover the through hull with shrinktape to help it not suck air when we craned in. Once the boat was on plane and running, it would blow through the tape and didnt matter. It was better than replacing an impeller right before the race. The Merc Racing ones solved all of that.
The Mercury ones use a 1in outlet hose.

Anyone have a link or pics of how these are plumbed in? I am running 30lb pressure on the gauges. Hoses are plumbed to side of block where the water drains are.

As the comment above stated, it's usually recommended to plumb the relief in between the cooler and the engine. You get the most cooling that way, plus the least amount of issues with things such as the strainer

I'm using a 1-1/4" coupler with a 3/4" bung for the relief valve. Same logic applies if using braided cooling lines, I'm not aware of any diagrams but I can scribble one up quick if it's easier to follow

The 3/8" water drains?

I can picture that, but where do you dump it over? Put a thru hull on the side of the hull or on the transom?

Curious your thoughts on what I should have mine adjusted to since they are strainer mounted. Thank you.

Yes
30 is fine as long as you have checked it to confirm

The valve is adjustable from 7-25 so 25 it is then. I think I set it less than 25 so thank you.

Strainer/ valve: Swirl-Away High Performance Sea Strainers - 1-1/4" NPT HO Competition Dual Strainer Basket Sea Strainer - 10" Tall - CP Performance

Valve: Water Pressure Relief Valve 3/4" NPT - Hardin Marine (hardin-marine.com)

I ended up putting mine next to the bilge pump thru-hull on the side by engine vents, anywhere would suffice though

That`s where I put mine , before it goes into motor, discharge on the side along with intercooler, bilge pumps, exhaust water .