What tools do I need to accompany OpenLayers to achieve what GeoExt is capable of? GeoExt can show frames of TOC, legends, etc.
And how about jQuery and Bootstrap combination? Can that became a replacement?
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So you want to create a heavy and dated looking panel based map interface? /joking/
Personally I would use Leaflet and JQuery. Both are very lightweight but have a wide range of mature plugins that can deliver what you need in a lightweight and modular way.
I don't think Bootstrap will be of much benefit. Map frames are pretty much responsive by default and Bootstrap is best used for web pages rather than small widgets which is what you tend to be making for web maps.
I use Bootstrap (and you can try the excellent BootLeaf template) to build a webpage with a nearly full-screen map. I've also used Bootstrap to build a single-page app with a smallish map.
You can also use simply Leaflet, and set up some buttons about the place using the built in controls, or roll your own user interface.
To answer your actual question, though, you just want to do normal web development and use OpenLayers functionality to handle the mapping. There is no generic user interface that will answer this for you. Either start using built-in OpenLayers functionality in a full-screen app, or write yourself a web page.