If you can get two high-temp threaded unions in that valve side-by-side, that is a great way to go. They seal with an O ring against the valve body. I still use three wraps of Teflon tape on those because I hate call-backs for a drip that might occur. In your picture the fitting on the right is CPVC. They work fine. I use a CPVC nipple as they are easier for me to obtain. Male CPVC adapter or CPVC nipple with a union at some point near the valve will work fine if you can't get 2 High-temp unions to fit.
Yes, sealant is needed (I use five or six wraps of Teflon tape AND silicone sealant over that) with the adapter and/or pipe nipple so that it won't leak. Will a leak occur at some point? Maybe. That's why unions are recommended. That way the fitting can be tightened a bit or removed and resealed if needed.
High-temp unions are threaded into the valve as far as they will go to compress the O ring. Pipe threads on an adapter or nipple should not be installed that far. They are tapered and either the valve, the fitting. or both will be damaged. Usually it is good to have no less than three threads showing when the fitting is tight.
These are an example of a high-temp union. You can see that the two nuts may not fit side-by-side in your valve.
Amazon.com: 2 PACK -CMP Hi-Temp Union 2" inch 2MIP x 2" inch PVC Whisperflo & Intelliflo - 2 PACK: Garden & Outdoor