Definitely go with quad shielded RG6 if you want to stay with 75 ohms. Home Depot and most local hardware stores sell this very cheap because it is the same one used by the cable TV industry.
The cost different from going to LMR240 usually isn’t large. It is a 50 ohms coax very similar in specs to RG6.
Each 50/75 transition can add 0.7 - 2dB of connector losses. This can usually similar to the actual transmission loss for a 25 feet coax cable.
Try to keep the antenna to receiver losses below 5dB in total (add up all cables and connectors losses). The lower the total losses the better.