Heliboard is fantastic ❤️

• glide typing.
• multiple languages at the same time (without switching).
• extremely customizable in nearly every way.
• customize long-press options for each key with multiple / list of options. For instance, I've extended the number keys row with my most-used emojis, so holding '1' gives me a pop-up with '❤️😍😘🥰', 2 gives '🙂😊😃😄', etc.
• 'snippets' via custom dictionary with shortcuts (typing 'xx' shows my primary email for 1-click insertion, 'yy' shows secondary email; endless possibilities). Possible with most keyboards, though.
• and so much more.

I haven't found anything that comes even close.