Only one thing:
if ISP 1 are not the same ISP for 2nd connection,
or you do not use another device on another part of the world to bond the two connection, or similar methods, etc.
30+30 never be 60Mbps
You are everitime limited to 30Mbps for connection.
With 2 ISP you have 30Mbps & 30Mbps and after some settings, the connection request can be “divided”, not literally, between the two ISP.
Your max speed for each connection still 30Mbps, but you can reach 60Mbps, for example, only downlading one big file using “multipart”
from two different sources, and each sources must be set to use different ISP.
To make it clear, you will have a TOTAL of 60Mbps for users to have access to but the max any one session can grab is 30mbps.
What I think you are getting at is that you want to use the WAN resources equally amongst all the users.
In other words if you have 120 users you want them to be able to access the full 60 such that if they are all on at the same time, 120/60 they should all be able to get approx 2Mbps for a session.
So that a combination of load balancing the WANS and queueing the LAN users.