Hello,
I'm using L2TP/IPsec VPN on RB5009. Can I set it so that there is only LAN access and the internet traffic works on the client side? Like OpenVPN, only access to LAN/subnets but internet connection is going through clien-side router. If it is possible how to configure it?
I have many VPN users - 15-20 clients works at the same time and all traffic goes through the VPN, together when YT is playing etc., it's heavy load for network.
OpenVPN is best for it but transfer speed is a half vs L2TP.

It's client-side option. E.g. if you have Windows, they for some strange reason (opinions about that may differ) assume that user wants to route everything over VPN. If you don't, you have to disable it, e.g. using PowerShell (unless you have some outdated Windows):
But then you may have problem with routes to subnets that you do want routed over VPN (depends on what exactly you have). In that case, look at Add-VpnConnectionRoute.