Messes up styling and Ajax MiniCart

Even with ALL modules disabled, it makes several things worse
without clearly letting the user know how to enable/disable this
(somewhere else than the modules, a setting or is it just a bug)?…

Like my (Block) theme and the Minicart from Merchant worked great
(+ a PHP snippet I had added to prevent items that I had limited
to max 1 purchase, to update the button and show it was already in cart),
adding items to the cart and opening the fly-out cart
on archive/shop pages, but now it has disabled that, and you get
an ugly inline “view cart” message beneath the Add To Cart button,
and no checkmark or text change to the ATC button after adding,
neither after refreshing the page..

…and it also doesn’t show a check-mark anymore
(plus I had the ATC button disabled after 1
of the same digital product was added to cart, and that’s also
gone… so there’s no indication for the viewer that it’s already
in their cart and only 1 can be bought…)

Then I look for a setting or module, but can’t find what’s wrong,
plus I disable all of them and purge cache and no change…!
Nor does this plugin give a better alternative in terms of
– a fly-out (Ajax) mini-cart
– and Ajax live updating of ATC buttons, when
a product has already been bought

So bugs, worsening experience, no clarity on what it’s doing behind the scenes,
illogical counter-intuitive choices and no better (instead worse)
in key areas than a free plugin and small PHP snippets I had already ??