corfu VS cape

You could try corfu. It has auto-completion disabled by default and works most places with M-Tab. Or you could set a longish corfu-auto-delay (0.75s say), and let auto popup only when you stop to ponder a while.

Corfu supports this. Or at least it allows you to move completions to the mini buffer which I find quiet useful.

A substantial section of the community is using corfu instead of company, but I wouldn't say company is out of date by any means. In emacs 29 eglot will be a built in, which might act as a replacement for lsp-mode depending on what functionality you need.

Wow, interesting that my response is getting down voted. It seems not enough that I give away my work for free. Nevertheless I appreciate support from the community, as other Emacs package developers. The support is actually helpful. To clarify, publishing my configuration would translate into quite a bit of work, requiring separation of private and public bits.

I am currently using evil and corfu, but I want to configure such that pressing a single escape will invoke corfu-quit when its UI is active (because pressing "C-g" is harder).

A few days ago I found an unexplained slowness when using Corfu on Emacs 29 with pgtk. I stripped my configuration to basically just Corfu, and still had a noticeable delay. Maybe it is related to your problem. https://github.com/minad/corfu/issues/307

The most straight forward solution is probably the package company-math. (that's what I use but with corfu and cape)

See here: https://github.com/minad/corfu/issues/231

Wow, interesting that my response is getting down voted. It seems not enough that I give away my work for free. Nevertheless I appreciate support from the community, as other Emacs package developers. The support is actually helpful. To clarify, publishing my configuration would translate into quite a bit of work, requiring separation of private and public bits.

At least for Elisp source block one can use font locking to create a custom Capf. Add cape-elisp-block from my Cape package to completion-at-point-functions. Even if you don't want to use Cape you could just copy it to your config. It is a short function.

You can use cape-history from my Cape package. This is similar to consult-history only utilizing completion-in-region instead of completing-read.

Haven't tried configuring it accordingly, but here's the docs: https://github.com/minad/cape

corfu is blazingly fast. Orderless is as well. What is not always blazingly fast is your completion providing backend. You didn't mention where your slow completions are coming from. An LSP server? Dabbrev? Maybe a remote machine? Have you combined results from various backends (e.g. using cape?). Some completions backends are unavoidably slow, others are just not well optimized.

The most straight forward solution is probably the package company-math. (that's what I use but with corfu and cape)

Some time I'll add a mixin for Cape which would make the completion stuff really nice.

If you're set on using the completion system (M-TAB) for this, you could install Cape and use the cape-abbrev command to complete your abbrevs.

Oh, of course your efforts are valuable. I didn't mean to sound discouraging in any way. The point made by /u/xenodium is good - if you have a special candidate source with special behavior, it makes sense to provide a separate lightweight Capf. In contrast, using Tempel for this purpose doesn't make much use of the actual template functionality. Tempel is only a good fit for Org blocks if you use it already anyway, as I do. There is also value in having reference Capfs around, which will be helpful when developers create their own new completion functions. This was also the intention when I created my Cape package, which comes with many simple Capfs. It is always interesting to see what other Emacs users come up with. I am thankful for such efforts - it is inspiring!