I see that there are many issues with win10/11 and drivers. I was wondering if I just use the USB for power and use an audio cable to connect the unit directly to my pc via the line-in?
If your goal is to use the device as an audio interface, then no, you cannot just connect a line-in to the behringer device. The device needs a way to send digital data to and from the PC- and USB is the only way.
With just a line-in- I'm not clear if you're suggesting a line from the behringer device to PC or vice versa. With PC to device, the only thing it would do for you is play sounds from your PC (or any other connected devices) through your headphones or speakers. With device to PC, you could record sound from a microphone or guitar, but only 2 channels at a time, and you can't play any sound through the behringer device. Monitoring will be a pain, and time delay compensation may be a pain as well. In both cases, you're just using the "direct monitor" feature to use the device as a preamp of sorts.
Using an audio interface as a USB-powered preamp is possible. However, it is not designed for that purpose, so results really depend on the particular interface. A principal difference is between (typically older and/or simpler interfaces) analog monitoring and "zero-latency" digital monitoring (where "zero" means actually something like 5ms, the time to convert samples from analog to digital including the necessary analog/digital filtering and back again and adding enough cycles for digital processing).
Sometimes interfaces offer channel inserts still in the analog pathway: those are also without either artifacts or delay from digital conversion/processing but offer only unbalanced connectivity.
Of course you cannot expect anything but the quality from the A/D conversion of the interface you ultimately use at the end, and integrated soundcard input quality is notoriously bad. Separate PCI soundcards will tend to be better but have to deal with being in the same enclosure as a lot of electric disturbances.
The price point of modern-day class-compliant audio hardware is such that you really should think twice before engaging in that kind of revitalizing old hardware. Sometimes it's just easier to sell the old gear to Linux users whose systems tend to have no more problems working with old hardware than they had 15 years ago.