Can I use an Apple 70W USB-C Power Adapter with a 13-inch, 2018 MacBook Pro?

Yes you can.

To realize full performance you def want to use a USB-C cable which can charge at higher rates. (not all can)

The cable that came from Apple with your MBP — if you still have it — is by definition suitable.

your computer appears to have shipped with this power adapter:

13-inch MacBook Pro models introduced in 2016 or later

Apple 61W USB-C Power Adapter and USB-C Charge Cable

Use a power adapter with your Mac - Apple Support

You can always use a Power adapter LARGER than the original. Your Mac only draws what it wants and ignores the rest.

USB cables that provide charging come in three flavors:

default 60 Watts

premium 100 Watts

super-premium 240 Watts.

for best results, use one rated higher than the default.

Yes!

No harm, the macOS can negotiate the proper wattage without issue.