What version of Remote Control did you install ?
To speed up the session start I would suggest you to get rid of the Java popup by installing the Controller application instead of relying on Java Web Start. In order to do that you can use the specific Task on the RC BigFix site or you can download the installer from the RC Server web interface (Tools -> Downloads -> Agents Downloads -> ). Then from the RC server web interface change
true on the trc.properties configuration. (Every operator have to install the Controller on the computer once this is enabled).
Your environment is quite small compared to some customer environment with 20.000 Targets and maybe more. However keep in mind that once that a communication between Controller and Target has been established there is no other component involved in the communication unless you use a Broker and you established a Broker session. In that case the Broker need to be capable of handling simultaneous sessions.
In general the number of the session that can be established simultaneously depends on how much hardware are available for the RC Serer and Broker and what is the bandwidth and latency between Controller and Target. In your specific case what are the operating systems involved in the session ? What do you mean with “sluggish” ? Can you be more precise ?