It may have been more useful to have already known that it would not be possible for Trump to do what you described.
"Not be possible" is too strong.
It's clearly possible unless Congress or the courts prevent it, even though it is clearly illegal. But Trump is doing lots of things that are clearly illegal, which is why the courts keep issuing injunctions to stop him (and then SCOTUS keeps staying the injunctions to let him go ahead and do it anyway, at least for a while). In a sane world, the fact that an action is illegal would be a stronger constraint because the president would have to be concerned that Congress would impeach and convict him, and he would have to be concerned about potential criminal liability. In the world that exists, the GOP leadership in Congress refuses to do their job to rein in the executive, and SCOTUS has declared the president above the law so there are few practical limitations on his power.
So far, the only thing that seems to really make Trump back off is when the stock market crashes.
Nevertheless, a slush fund of several billion dollars per year that the president is truly able to spend with complete discretion would be a significant additional increase in power because it's not clear that anyone would have standing to sue, so courts could not intervene regardless of constitutionality. Congress would be able to intervene, of course, but, again, the GOP-led Congress has almost completely abdicated. I had to add "almost" only because they actually did stand up to him on the Epstein files (sort of; the bill left Pam Bondi with near-total freedom to withhold anything she wants, not legally, but practically).
Trump is more open than other Presidents.
No, Trump is more secretive than most other presidents. You're confusing "unfiltered and disorganized" with "transparent". I do have to grant that he's incredibly transparent about his corruption. Well, maybe. He has been transparently corrupt in lots of ways, but it still seems likely that there's more corruption which he's keeping hidden.