Re: 7420/7620 necks
The TRS is fine if you're not a Vai-esque divebomber. If you're a casual trem user, a TRS-equipped machine is fine... but if you abuse the tremolo, the TRS is not for you. I have an S470 with the 6-string Lo-TRS. It's fine, but it obviously can't handle the abuse my LPE/EdgePro equipped guitars can. I've heard many times that the OFR is a direct replacement for the TRS system, but I haven't tried it myself nor do I know of its stability once you perform the upgrade.
The 7420 I played was a great entry level guitar, but if I were looking long term, I'd go after a 7620 or UV. Those are professional-grade instruments with top-shelf hardware designed for stability when properly cared for.