In broad strokes, I am looking to prototype a Teensy-based solution for 48/60 MHz data acquisition from 1-6/8 infrared sensors using FTM, using Teensy LC and/or Teensy 3.6.

Something using a Teensy that looks a bit like

The input signals are going to be pulse trains from 15-150usec, with a carrier frequency of 1-10 MHz. The job of the Teensy is to read a minimum of 3, and up to 6/8 of those input channels, and for each pulse train calculate first/last edge, average/min/max edge-to-edge interval. Pulse trains are expected to occur with a rate of at least 240Hz, would like to handle at least 4x as much, but can go below 240Hz, as low as needed. Pulse trains can be back-to-back in some cases (or overlap, in which case I need to early reject), and I need to tell them apart by carrier frequency. I am free to reject as many pulse trains as I have to, as long as I ensure I don't reject the same ones over and over, so overrun on a ring buffer or dropping events to complete processing (and serial communication) is not a problem. I might even move the actual data processing on the Teensy to alternate with acquisition.

I'll wind up with a few variations of the same components. The sensor parts will most likely be sourced here:

Each sensor runs 4 wires - two I/O to Teensy, plus 3V3, GND. One of the I/O channels (each) will be captured using FTM, the other might be using GPIO or FTM depending on total number of sensors (3 vs. 6 for LC, 4 vs. 8 for 3.6). I might be using ribbon soldered to PCB test points or use their FPC/FFC connections, so I'll be looking into making a simple OSH shield to handle the max 8x2 plus GND+3V3 connections, either with solder pads or FPC.

Question(s) 1: mechanics. I don't want to exceed the 17.78mm width of the Teensy for any shield/breakout/passthru. I also would like to not exceed 12mm in total "stack height" in the end, of which the Teensy uses about 5mm by itself, but for now that's negotiable (as is the width, if it gets me off-the-shelf-shields to start with). I can extend in length as much as I want to. What's the best setup for a Teensy shield to connect to Teensy - which header/pins to use? Lowest height profile? Is there a perfboard that has the same width as a Teensy and fits on it? Anybody know of e.g. an OSH perfboard-style "shield" made for Teensy I could mod or use as-is?

Question(s) 2: per spec, each sensor draws a max of 7mA at 3V3. At 8 sensors, this would be less than 60mA. I hope to power the sensors from the Teensy 3V3. What is the max. 3V3 output from an LC? Table 2.9 p. 48 says 120mA, am I reading this right? For the 3.6, Table 2.9 p. 82, says 150mA, is that correct? ? Is that regardless of how hard the processor is working? How much does an LC or a 3.6 need going all-out? I do not plan on overclocking, but I assume that would reduce available current as well - linear or squared?

If I wanted to power the sensors separately, what is the simplest way to provide 60+ mA of 3V3 using the same 5V power as the Teensy. As a bonus, what's the simplest solution to turn that 3V3 power to the sensors on/off (the sensors might have to be power-cycled for certain failure states)?

The tech specs here
either don't state the max. 3V3 output, and I saw 100mA for 3.0 and 250 for 3.5 on the forums.

Question(s) 3: I am looking for an inclinometer solution, that is, I want the best possible read for local gravity at rest. I'd settle for an accelerometer with high resolution but minimal range (handles 1G plus to avoid clamping at rest, not more). I'll start with an IMU, if there is an existing Teensy shield for it. An open source inclino/accelerometer-only board would be perfect to start with, because ultimately I might want to put the inertial sensor on the DIY shield with the other connectors. I saw mention of the ADXL345. Is there a(nother) good off-the-shelf product for Teensy to start with?

I'll try the prop shield in any case, as I want to experiment with LEDs as well, but it's overkill for what I need:

This is for the static case, so I find myself in the situation that I have use for accelerometer and possible magnetic field sensor, but no use for gyro, and I need resolution and low noise over range. If the best solution is to use an IMU anyway, I can settle for that. Is the MPU6050 a good/the best option to start with? For the future, is there a solution powered from the Teensy 3V3, and how much of my output current budget will that cost?

Question(s) 4: I might want to use remaining Teensy GPIO to control/power on/off whatever number of IR LEDs I can support. I expect that I will need separate power for that, so I'd appreciate a recommendation for an open source LED driver solution that can be controlled by the Teensy. In the simplest case, there'll be about 8 LEDs, all either on or off. In the most complicated case, I'd try running a number of LEDs lit in different combinations (some on, some off), combinations changed at 60Hz, and/or modulate each LED with a 1-10 MHz carrier frequency, and/or use 10-200usec flashes. I might try to do whatever subset of the LED functionality a Teensy can handle directly, just using the spare GPIO (and 3V3 power). I am free to alternate "LED mode" with "sensor mode" - I can even alternate "tilt[+mag]" mode, "sensor mode", and "LED mode", and "batch-process mode", as I operate strictly at rest - so as long as the Teensy can handle capture and power for each of these modes on its own, it'll just take me longer to do what I need.

Any suggestions, hints, references on any aspect of the above appreciated.