The console command flareconfig 0 tex 2 activates the flares that have rings (put that in autoexec.cfg for it to run automatically; remember that autoexec.cfg should be in your runtime directory Run\jDoom\). The default lens flares are activated with the command flareconfig 0 tex -1.
Add these lines in Defs\jDoom\User.ded if you want to make the health bonuses a bit brighter: (if User.ded doesn't exist, just create a new file)
Light { State = "BON1"; Size = 0.7; }
Copy Light { State = "BON1A"; }
Copy Light { State = "BON1B"; }
Copy Light { State = "BON1C"; }
Copy Light { State = "BON1D"; }
Copy Light { State = "BON1E"; }