I did 3 years as a staff nurse before traveling at a teaching hospital. Before I started travel, I tested my skills by doing "local" per diem at other hospitals first. That completely reassured me that I would be able to adapt anywhere, and I have. Mind you, there was no EMR back then (paper is easy) and some of them are insane. Last place I worked did Epic for the first time, not really so hard I suppose, but other travelers told me this particular facility did double the "pages" as other Epic ORs. If I hadn't been doing CVOR with relatively long cases, I'd never be able to finish by the end of the case. And in 25 years of traveling, that would have been a first for me. It was compounded by the week of hospital (no OR) orientation where the IT people did not have a working OR training software.
So not really here to tell you about one hellacious start to an assignment but every hospital is very different (also surprising how many ways surgeons do the same surgery) so it really helps to have your clinical skills down pat. So if you are at all insecure, yes, do another year of staff. Not that many OR assignments right now anyway for the first time in 25 years of my own memory, too many elective surgeries cancelled to have much need for travelers and those assignments are really competitive!
In my 25 years of travel, I've never been thrown in without sufficient orientation - at least for me (shortest ever was 4 hours, but that was back when open heart was easy and everything was a few feet from the room). I personally learn a lot faster if my orientation is shorter - when a surgeon is yelling at you for something, you really remember where that supply is! And that is the major reason why OR nurses typically have longer orientation than other specialties, you have to learn where thousands of items are and retrieve them on a surgeon's clock (which as you know is at least 4 times faster than real time). One thing some hospitals do is have you pull cases during orientation. I volunteer to do them if a hospital isn't organized, a great way to learn the place.
As far as EMRs go, don't worry about it. Most hospital orientations train you for at least three days on it, much of it completely wasted in the OR. I've done a lot of EMRs, including Meditech before IBM compatibles before they had mice - all keystroke navigation. Documentation is far less in the OR than most specialties and I try to skip most of the hospital orientation and just learn by watching in the room.
Most travelers (not just OR) feel like hospital orientation is largely a waste of time. You will also get at least three days, usually a week, to orient in the OR.