Is there a way to get to the sysctl or procfs settings?
Would love to set net.ipv4.tcp_slow_start_after_idle=0 as well. 
and disable “lazy” conntrack behavior, yep )
Some of those settings are available at a few different pages in the gui, but there does not appear to be a low-level
direct access.
This is the normal situation for MikroTik routers: it is a Linux platform but it is well hidden for the admin.
That makes it “easier” to configure, although one or two times I had to search quite a lot to achieve something that I already knew would be easy on a bare Linux system.