Is it possible to configure Lubuntu so that I can open folders or run applications with a single click instead of a double-click? Thanks in advance.
Yes, you should be able to do so. Open PCManFM which is the default file manager. Click on Edit, Preferences, and then tick "Open Files with Single Click". That's all.

If you prefer to do it through command line (like I had to, due to a small resolution touchscreen and the need to script it for creating additional devices), you can modify the /home/pi/.config/libfm.conf file.
Change line 5 of this file from single_click=0 to single_click=1.
You will be required to restart your machine for this to take affect, so I gave it a sudo reboot after saving the change.
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This file explicitly says
# Autogenerated file, don't edit, your changes will be overwritten., are you sure it should be edited? – Shelvacu Aug 24 '17 at 13:05