they're better place in the apiary or ... nearby?
There will be some that will recount swarms arriving within the apiary. It will happen. Happened to me last year - and wasn't into a bait hive, either.
However, think a bit about what the outcome of colony reproduction should achieve - dispersion of the species and non-competition for resources are two sensible achievements. That does not lean towards in-apiary occupation.
or just somewhere else nearby?
No, it needs some thought and consideration; 'just' somewhere else may be entirely inappropriate. Most references I have seen are for about 200m distant, but less than a kilometre.
Does it have to be closed floor
No, but it is preferable if you wish to improve the strike rate. An upturned dustbin could be tried and might get occupied, but....
does OMF work as well?
No.
has anyone had a problem with wax moths from leaving old brood comb?
I daresay there are some. Personally, I don't leave them unattended that long, do not have a pandemic of wax moth around my sites and have never suffered with wax moth in a bait hive. If wax moth is a severe problem then spraying the frames with Certan, before putting them out, would perhaps be appropriate?
All fairly basic questions and I have outlined my reasoning. Now, do you have any that need some real discussion?
RAB