On the Series 70, little needs to be done to make a primo carry and defense weapon. The trigger usually needs a little attention, sights should be large and capable of fast acquistion and feeding has to be reliable. A good smith can do all of the above.
Back when the model came out, there was some negative stuff about one of the fingers on the collet bushing breaking occasionally. The furor seems to have died down, but changing to a well fitted solid bushing will fix. OTOH, I shot mine through about 8-10,000 rounds in one year and never had a problem. Mods were limited trigger work and the installation of large, fixed sights.
The above info about reliability is excellent. Usually, s little polishing of the feed ramp is a good idea, and relieving the ejection port helps. BTW, if your brass is dented on one side after firing, relieving that port should fix.
As for ammo, there's not any bad 45 loads out there. Pick a reliable soft nose or HP that groups well and be easy in your mind. The piece will do its part if you do yours.