I like Bachmann's screw connectors.
Bachmann sell the screw type fishplates separately. I have had good success using an inexpensive drill press to drill holes in the rails and then tapping the hole. Aristocraft track also uses the screw type fishplates, if that is available to you. (No idea how to translate this.)I like Bachmann's screw connectors.
Thank you your info is very valuable, I also have a mix. I will tryYou could use Massoth type rail clamps Google Search for a good stable and conductive connection. I have a mix of LGB, Aristocraft and Bachmann rail/track on my layout all perfectly compatible for mixing. Max