Well the combination of N,N-DMT with either dextroamphetamine, 4-fluoroamphetamine or 2-fluoroamphetamine make the 'zooming' velocity and that of my general train of thought even an order of magnitude higher,however most spiritual aspects are lost in turn for a clarity of mind similar to what limited experience with DOX showed me. I distinctly recall images flashing before my eyes maybe even like 30 Hz, of random objects and people and places - no apparent connection whatsoever. A strange thing about this is that I have experienced the exact same before with not more than a handful of times with cannabis, IIRC most likely when getting hit hard with very low tolerance.
N,N-DMT can give me mini-episodes of panic involving forgetting how to breathe properly: not too deep, not too shallow, not too fast or slow. Usually this is quite minimal and a transient phase associated with being overwhelmed at the very peak. Amphetamines amplify this unrest a lot for me. All normal ones do, but MDMA is very different. With DMT it did not give me uncomfortable side-effects or if it did I was too euphoric to mind, also it helped take almost all general fear away. Even though it was great, taking MDMA for the sole purpose of taking your DMT fears away doesn't seem right to me. Fear and darkness - though with moderation - deserve to be part of the big picture, as part of dualism.
An experience with 4-AcO-DMT and methylone (among other things) ended me up at the ER with a panic attack that escalated by blood gas concentrations. While it is a complex story, I feel like the residual anxiety contributed by methylone was part of the problem. Avoid that when your psychedelic effects are scheduled to continue.
I'm not sure how often in total I have taken tryptamines with amphetamines or tryptamines with stimulants in general. In retrospect I would not recommend it to be honest.
aMT which is chemically a hybrid between amphetamine and tryptamine, that I find wonderful. aMT, I definitely would recommend.
But looking at your more specific example of adderall and 4-HO-MPT, let's start by asking why you would want to have the adderall in the mix? Is it prescribed to you and are you always on it? If so, I think it should be okay but just don't take anything more than a 'maintenance' dose of adderall. Just enough not to feel weirded out by the change in your state. Reconsider adding a bit extra to make it extra superduper nice.
With amphetamines there is first (at quite low doses) that feeling of having more space and fresh air in your mind - a feeling of open room in your head... at least IMO/IME, if the dose is higher than that I start to feel more and more driven. I think that this element of stimulation can in best cases color your headspace and make it feel like you are less 'pure', perhaps intoxicated is the word. In worst cases especially if the trip is also strong, stimulation could add extra overdrive.
But, having given my opinion I should say: I have limited positive things to say about stimulants and would not call myself a speedfreak type of guy. Perhaps if you are, you like your speed together with virtually any other drug. And the same could be said about serious opiate users: for them it might be much more normal to combine opiates with anything else that is used.