TWC in my area is getting MAXX. Speeds up to 300/30 Mbps. I am due to get 200/20. However, TWC won't do that on my SB6141. It isn't that the modem can't support it, it is that they won't deliver it through that modem. They have a list of supported speeds through various modems. I will have to upgrade soon.
I got and hooked up the SB6141 back in 2013 when it was still Motorola. Luckily for me I purchased it for 70 bucks on sale. It is one of the best things I have done. It works great with Time Warner and have never had an issue with it. I paired it with a NetGear wireless router and saved myself 12 a month at the time. Now that price would be almost 20 a month for the pair. I highly recommend getting your own modem and router. It paid for itself in less than a year.
Do these modems work for telephone through cable? Specifically for Comcast?
Are you asking about an instance where you've bundled phone and Internet service? In this instance, your Internet/phone provider often uses the same device to deliver the phone and Internet service. You'll want to contact them directly and ask, because it may be a situation where you'll still need provider-supplied equipment.