What is your opinion on OpenVPN GUI vs OpenVPN Connect vs Wireguard app?

As far as I know OpenVPN Connect is not open source. So

Question 1. Which would you recommend between OpenVPN GUI vs OpenVPN Connect? Is OpenVPN Connect being a closed-source app an issue for privacy?

Question 2. Is it recommended not to use OpenVPN GUI, OpenVPN Connect and Wireguard app if VPN provider’s app is available on my platform?

Thanks.