Thanks Waqar! I just called up KCS in my area and spoke to the guy incharge and he first gave me a lecture on how experienced he is in cable operations and then said that both rg6 and rg7 are fine as long as they are "copper" and that they installed the best quality of cable in my house. He said that I shouldn't worry about rg6 and rg7 as the rg6 he installed is better than rg7, otherwise he would just tell me the price difference and install rg7 but he said that it's not required.
I then called up Solo on their direct number and spoke to someone who also confirmed that rg6 cable should be fine. He was surprised to hear that my box is receiving 111 channels because he said solo is only providing a max of 98 channels! He then asked me to do a "delete all channels", do a "restore factory settings", then re-tune using auto search, then go to Star World from the list and allow the box to automatically update the channel list. This way, the list went back to the 98 original channels that solo is providing from its headend and these channels have no distortion overall.
So I guess my cable wala was also right. The distortion I get is only on channels that someone else is forcing into the system from their own headend (probably KCS like Ali pointed out). On the original solo list of 98 channels, there's no WB or Sony Pix (WB) or mbc max or any local channel like Express News. These are the channels which I get distortion on. Quite surprising because if you run an auto search, the box automatically receives the extra channels but apparently the extra channels are not from Solo but being input by local cable operators themselves. Also, Solo quite proudly states that their box does NOT include any local channels and they're showing only international channels. So these channels (mostly local and some others like WB and MBC Max) are obviously not from solo.