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This is nasturtium, Tropaeolum majus. Here is more about it:

https://www.gardeningknowhow.com/ornamental/flowers/nasturtium/growing-nasturtiums.htm

Yes, you can pinch out the growth to keep them from becoming too leggy.

https://www.gardeningknowhow.com/ornamental/flowers/nasturtium/growing-nasturtiums.htm

Yes! The bright yellow and orange flowers (and several other colors!) are great pollinator magnets!

The nectar in the flowers is very tasty!

https://www.gardeningknowhow.com/ornamental/flowers/nasturtium/growing-nasturtiums.htm

It is common for some leaves to yellow on a Nasturtium. They are fast growers and the plant often shades itself. Just pinch off the leaves.
If it is more then the occasional yellow leaf, check your watering.
Too much or too little can cause yellowing leaves.

https://www.gardeningknowhow.com/ornamental/flowers/nasturtium/growing-nasturtiums.htm

This can happen when they receive too much shade. They are suited for full sun, and only partial shade. This could also have something to do with poor soil fertility, or compacted soil as well, although soil fertility is not a usual problem. They will thrive in low nutrient environment just fine, usually.

This article will give you more information on their care: https://www.gardeningknowhow.com/ornamental/flowers/nasturtium/growing-nasturtiums.htm

I think trailing nasturiums will be perfect for this application. There are even black varieties, which I like to seed every year, that are very interesting. This article will give you more information on the care of these: https://www.gardeningknowhow.com/ornamental/flowers/nasturtium/growing-nasturtiums.htm