#1 - forget NMEA2000. not important
#2 - VE = Victron Energy;
#3 the .Direct, .Can and .Bus after the VE part - just different connectivity standards used by Victron products. Think of it like Video Tape Players. These may have a SCART connector, or a Composite Video connector or an HDMI connector depending on age or model - different cables to connect something to a TV to watch a video. Just alternative ways to achieve the same goal. Same as the Victron kit and their standards.
There are obviously technical differences between the different connections and what they can do, but which one you use depends on what the product is. You don't get to choose the type, that depends on the device you have (have a look here for a list of the most common products and what cable standard it uses -
https://wildebus.com/store/index.php?route=product/product&path=83&product_id=136 . It is not a complete list (inverters for example have a variety depending on model and age))
Two ways to talk to Victron Devices remotely
a) Bluetooth - using Victron Connect App on Phone/Tablet
b) Wired via Cables to Venus Device and then view - via Wireless/Network using Victron Venus via Web Browser
Typically you would only use a wired connection if you are connecting a device to a Victron Venus device (Venus devices are the central hub which reads the data from devices connected to it and records it).
If you don't have a Venus device (Venus GX, CCGX or a Raspberry Pi maybe) then you would use the Bluetooth Victron Connect method. There are only two common things you would get that involve worrying about those cable standards when using Victron Connect
1) VE.Direct to Bluetooth Dongle - use to add bluetooth capability to VE.Direct devices that don't have it
2) VE.Bus Smart (Bluetooth) Dongle - same as above but for VE.Bus devices
Finally, if you don't use Victron Venus or Victron Connect, you would use whatever switches/buttons/jumpers on the device to work it manually at the device. In this case, the unit is standalone and the cable connection type is irrelvent.
HTH