Texpad (https://www.texpadapp.com) most often; I like the editor, it has syntax highlighting and shortcuts. You can set it to auto-typeset as you type and it can sync the PDF with where you are in your TeX file. I use Overleaf (https://www.overleaf.com/) when I'm collaborating with others.

Atom (https://atom.io/) and Sublime Text (http://www.sublimetext.com) will have plenty of packages that you can install to make it more IDE-like.

Emacs. Edit your tex file, start a shell buffer, and start your dvi browser. Now edit the tex, run latex in the shell, and you get to see the dvi output. Repeat until done.

I have tried this with vim, but there are a lot of things lacking that an IDE could provide - code completion, searching of references, overview of the whole document, auto closing of blocks etc. It's probably possible to set something close up with vim but it would take a while. Maybe emacs has better tex support?

I use TeXStudio.

Currently, I am working on my undergraduate thesis book. TeXStudio is like an IDE. It supports syntax highlighting, code completion, source code and PDF synchronizing. Beside that, you can even paste your external image file that to be included in your LaTeX document (TeXStudio will help you to generate the graphic syntax with additional parameterms, like width and height).

Give it a try!

I use Emacs' org-mode for data science and for math courses. With Babel you can evaluate code and see the results in-line, with syntax highlighting. I don't use code completion myself but I'm confident it's available. With LaTeX preview, you can see mathematical formulae pre-rendered, again in-page.

You can then export from org-mode to LaTex, defining all the relevant settings at the top of the page.

I haven't tried it on documents that'd be as long as a Thesis, but I've happily used https://www.overleaf.com/ for docs up to 20 pages. Lots of universities use it, so you might even get a discount for the "pro" version (basic version is free).

Give texstudio a try. I find it offers exactly the kind of IDE-style features that I was missing from Emacs and other editors.

Sublime text on ubuntu. Works like a charm, I'm actually using it for a latex document.

texworks or textudio/texmaker the last 8 years.