You can connect without nuking your heads they aren't power they are data only the heads might steady burn (patturn freeze) till you unhook them at the worst i personally never seen a sync wire kill any head or flasher unless power is applied to it just read the manuals incase there's a need to set anything as a slave and master (federal signal and feniex are 2 brands i know that are configured this way)
I'm trying to find amber/white Mpowers myself if I get them before you solve this issue ill test out the sync for ya