1. I have clear routers RB2011 and RB750GL, there is no configuration at this moment. So i expect, that also VLAN 101 should be created for the IPTV traffic. What is the best option of creating the VLAN configuration? Do it over the switch or the old way?
Be careful with RB2011, it's got two switch chips (one for gigabit ports and one for fast ethernet ports) and if you'll configure VLANs on switch chip, things might get complicated - specially so if you're going to span ether ports from both switch chips. If you go with the new btidge vlan concept, things will stay (relatively) simple at expense of performance.
For the RB750GL I'd suggest to use switch chip, its CPU will struggle if configured the new way.
Anyway, have a look at
this thread, it makes great reading about vlans configured the new way.
Regarding VLAN101: it depends how IPTV gets delivered to the left side of RB2011 ... if it's tagged already (probably meaning that STB expects it tagged as well), then you need one ether port on RB2011 as tagged (trunk) port for that VLAN (but in contrast to ether4 it shouldn't be member of VLAN13). Depending on STB ... you might want to deliver internet connectivity to it. Might be that STP expects untagged internet, so STB-facing ether port on RB750GL should be hybrid port (tagged for VLAN101 and untagged for VLAN13).
If IPTV is delivered untagged (and STB expects it untagged as well), then port on RB2011 should be untagged access port for VLAN101, STB-facing ether port on RB750GL as well.
2. The LHG 5AC is already configured as a bridge, should i define all the vlan details or is it better to keep it in default bridge configuration and do the vlan stuff on the second router (RB750GL)?
The steps I described were for RB2011 and the left LHG 5AC ... And I described what I consider optimal LHG config. You can keep it in "more transparent" configuration regarding VLANs by ommiting all VLAN setup (only vlan interface on bridge is needed for management access). Whatever config done on RB2011 should probably be mirrored on RB750GL.