Sgt, it will 'more-or less' work fine. As I said in a similar thread here, about a week ago I use 3 monitors on a system with 5 available video outs. I have two calibrated LCDs and an old CRT, that I use for junk display, clocks, emails, handy references, etc.
The primary issue is that by default LR wants to put the secondary display on the old CRT.
I work around that by opening the secondary display at *not* 'Fullscreen' mode, and then drag it to the proper monitor. Once there, LR remembers where I left. I then size it as large as it will go.
I fiddled with video adapter arrangements, and switched cables and jacks, etc, for quite a while, but ran out of patience before I resolved the issue. My workaround suits me, fine.
See this
thread.
You won't be able to use LR on 3 monitors simultaneously. Well, that's not strictly true, if you have LR set at less than fullscreen mode, you can drag either the main or secondary windows either wide or tall, to occupy more than one monitor display. Some foks do this to move the panels onto a secondary display monitor, to allow more space in the main display area.