You can use the
anntenaweb.org website to get a prediction of what channels you can get and what antenna you need.
I'm not sure who your internet provider is. If you're still getting internet access from the cable company, you'll need their cable hooked up to your modem/router, otherwise you can disconnect the cable input from the first splitter and connect your antenna there to use your existing wiring to get the antenna signal distributed to all your TVs. Of course splitting the signal weakens it, so you may want to add an amplifier before the splitter or choose a larger antenna. If your antenna is outside, be sure to ground it to reduce the risk of damaging your equipment.
There is no such thing as a "digital" or "high definition" antenna. Antennas are simply designed to pick up certain frequencies. Before digital TV, many of the most popular stations were on VHF channels 2-13, so antennas were designed to pick up these frequencies well. When digital HDTV came out, stations were allowed to add a digital signal on a UHF channel (digital channel numbers you select do not need to match the radio frequency used) and many antennas designed to pick up these channels were marketed as "digital" or "high definition" antennas. If some of your stations moved their digital signal to VHF frequencies after the transition, these antennas may be worse for getting their signal now than an old "analog" antanna. For me the two stations that moved their digital signals to VHF are the most difficult to receive because modern antennas are frequently designed primarily for UHF reception.
VHF antenna: Typically long linear horizontal elements perpendictular to the signal. The array of varied length elements that make up the triangular shape of traditional rooftop antennas and the FM radio like whips (FM radio is between VHF 6 and VHF 7, analog TV audio is FM radio) of traditional rabit ears are designed for VHF. Because the lowest frequency/longest wavelength channels were removed from broadcast TV, a VHF antenna designed after the 2009 digital transition can be significantly smaller for the same reception of the remaining channels.
UHF antenna: Usually a variation on a Yagi design (lots of short linear elements about the same lenght in a row pointing at the signal at the front of traditional rooftop antennas) or grid/loop that faces the signal (the loop on traditional rabit ears, various grid design "high definition" antennas).
Well in between all this I went and got a Digital Antenna. For 50$ I get two major city networks I am in between and holly molly why did I wait so long. This picture in some cases is better than cable was and I get over 60 channels!
Yes, the primary channel for most broadcast stations can be better than the cable signal for those stations.
Since you are between two major cities, you may be getting some channels that are not officially licensed to cover your area. The FCC may not protect your reception of these channels in the spectrum repacking that will start in Fall 2018.
