Part: The First.
Part: The Second.
Part: The Third.
Does this look ok for a simple obstacle-avoiding bot before I commit to getting the remaining parts?
Thank you 
I’m still wrapping my head around those differences etc but thanks for the detail.
I guess for a hobbyist, you can only trust what you find online - but there is SOOO much conflict and misinformation that it can be tricky.
And I don’t think it’s unfair to wonder why I find 4xAa batteries at ~2000mAh each would struggle to power an Arduino and a couple of small motors & servo yet a single 3.7V, 500mAh battery could power so much inside another robot running an OS with way more devices, sensors, etc (though Jim addressed that point somewhat).
Cheers
Yes. I am, it would seem. But previous comments mentioned voltage requirements, ie 7V min. So I ran with that and asked the “why” question. How silly of
me.
I appreciate you taking the time to input, genuinely, where helpful. But when it results to condescending, then (to quote you back) “it is silly, and accomplished nothing useful”
I’ve had a few (general, non robot) kits from Elegoo recently and have been impressed. I shall definitely look closer, especially as many of the parts I have now already are used in these robot kits too so perhaps more easily relatable!
Cheers
Best to find a good text book rather than online subjects until you know enough to tell the difference.
In that case you need to observe the data sheet minimums and maximums and begin to think about buck/boost converters. The so called Maker community has, in a sense, done a disservice by publishing cookbook projects without trying to educate, as well. People build and fly an Estes rocket and suddenly they're rocket scientists. 
Ha exactly!
I think it’s the bar of entry too. If you want to make a breadboard computer, there are a few series - because it’s hard and precise! But with robots, one video shows you how to glue a motor to a volatile battery with a couple of wires, with a glue stick and some card, and it’s copycat across many many videos and articles all regurgitating the same misinformation.
So obviously I want to do things a little more carefully. I have a curious daughter thats fascinated by some of this stuff so clearly I don’t want things going wrong, melting, etc 
So what are your final plans?
Concede briefly and take a step back
I think it’s clear that I underestimated the overall project despite seeming simple-ish.
Whilst copying other projects might get people started, I’d prefer to understand what I’m doing and many are very much “here, glue this to this and watch it go!” with very little info. I’ve already (accidentally rather than by wiring things up wrong) melted the end of a battery holder - which is certainly NOT what I want happening inside of a finished project. Lesson learned not to leave batteries in when not hooked up/in use
I can fairly comfortably get the individual parts working well together via a mains power supply, and code isn’t a problem. Different sources of power is, so I think:
-
a good bit more reading up on powering these things. Batteries. Sort out my voltages/currents and terminology
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some of the Elegoo projects (suggested above) are quite decent at also providing details so I could do worse than taking a closer look there
Can't argue with that school of thought.
If you have the time, I recommend this website for learning basic electronics.
https://www.allaboutcircuits.com/textbook/
P.S. Fritzing is OK with me
I have the time even with a cursory glance it appears to cover much of the stuff I’m struggling with in detail but without being baffling! So thank you for that! I’ll be sure to have a good read.
I have personally read through much of the material to make sure it's not a bunch of BS. No-nonsense and straight forward, it's the best I've found on the net.
Have FUN!
Try this step-by-step to program each device on the bot...