The preferred setup would be the preamp as close the TT as practical, then the amp/receiver can be further away.
My TT's are connected to the Preamp with a little more than half a meter of cable and then preamp to the receiver is roughly a 6-7 meters:
(my preamps are the two black boxes in the center between the TT's)
The reasoning is the TT puts out a very low voltage signal, so you don't want it to travel any further than it needs to reach the preamp. The preamp sends out a line level signal, which can deal much better with the losses that can be encountered traveling a larger distance. It's all about feeding your amp/receiver a good, strong, clean source signal.
Interconnect is the RCA cable. Bascially, anything that's not speaker wire to the speakers is an "interconnect". An interconnect "connects" all your various pieces of audio equipment to the receiver/amp. I make my own cables, but you should look for good shielding, decent wire gauge, good strain relief, at least gold plated ends and good solid rca connectors that won't go "weak" after a few disconnection/re-connections . If they list it, you should prefer internal connections to be soldered for long term reliability.
Higher cost does not always equal higher quality. Nor does thick heavy cables always mean high quality. I build my own, so I can't recommend a particular brand.
You only need to "ground" the TT to the first component in the chain to eliminate "hum". In this case, that would be the preamp.
Good luck.