1. when I set RUTX09's modem to bridge mode and modem is still not connected, end device would get local IP from rutx09 - this, of course, would not change immediately once modem is connected, so I either need to wait until dhcp lease expires or manually restart wan interface of end device. When I disable DHCP on rutx09, I would not get ANY IP on end device. Workaround seems to be to leave dhcp enabled, set start ip "1", limit "1", so it'll have both start/end ip address both 192.168.1.1 in DHCP settings on lan interface - in this case, my end device wan interface only receives IP from ISP once modem is connected. I don't have to remind here that with local IP in bridge mode, internet connection does not work. Similiar behaviour is with passthrough mode with exception that when I get local IP, once modem is connected, internet connectivity works as it does NAT.
2. In passthrough mode (which is the one I'd like to use to have internet connectivity to check/update firmware of system/modem, when I get IP from ISP, my upload is cca 40mbit/s, when I receive local IP (when modem is not connected yet), my upload is about twice lower = 20mbit/s, can you explain what's happening there?