Let me see if I can help demystify this a bit.
Let me start by apologizing for the length of this post. There is a lot to cover, so if I confuse you, please feel free to ask questions!
The first thing you need to be keenly aware of is that up until EXTREMELY recently, a 130W USB-C adapter was considered "non-standard". Let me explain....
Laptops that use USB-C power connections are very different from laptops that use a barrel connector. On laptops using a barrel connector, all that matters is that the AC adapter has the right voltage and that it can put out sufficient current to satisfy the needs of the laptop. With USB-C, there is a lot more involved. Yes, the AC adapter has to also support the correct voltage and have sufficient power output, but the adapter that you are using must support the PD or "Power Delivery" protocol. Put another way, a USB-C power adapter can typically output multiple different voltages such as 5V, 9V, 15V, and 20V. When you plug that adapter into the laptop, it uses the PD protocol to communicate back and forth between the adapter and the notebook to negotiate the voltage that will be used.
You can purchase AC adapters that can output different amounts of power. Some might support something like 20W or 30W. These are typically used for smaller devices like phones. For laptops, the typical chargers are 65W, or 90W, 100W. If you use an adapter with a lower wattage rating it MAY work, but it obviously charge the battery more slowly. For a laptop that is very busy, drawing near peak power it's possible that using an underpowered charger may not keep up with the amount of power being drawn by the laptop, in which case it simply will not charge, or it may charge very slowly.
Let me give you an example:
I have an HP laptop. The original USB-C charger for it was a 90W charger. It died. I started using a 65W adapter with that laptop, and it worked fine, it just took longer to charge.
Now, here is another wrinkle. Remember that we said that the USB-C adapter should be capable of supplying enough power to the laptop. With USB-C you also need to make sure that the cable is capable of delivering enough power! Yes, that's right, the USB-C cables have a chip built into them, known as an e-marker, that communicates with the charger and tells it how much power it is capable of delivering. These cables are typically rated for either 65W or 100W.
So, let's use another example: I have my HP laptop and a USB-C charger that is capable of delivering 100W of power. I connect the charger and the laptop with a cable capable of 65W. This means that even though my charger is capable of delivering 100W, the most power that will ever be sent to the laptop is 65W.
Now, we introduce yet one more layer of complexity: Up until EXTREMELY recently, the USB-C power delivery (PD) spec only allowed for 100W max. The brand new PD 3.1 spec allows for up to 240W but you need cables and chargers capable of this. How new is this standard? The very first products to support this standard are only just now hitting the market.
So, the fact that Dell is using a 130W adapter makes me a little worried that it may potentially be proprietary. My guess is that a 90W or 100W charger / cable will probably work fine, but I would urge caution.
Since you are working with something that has the potential to be non-standard, you might want to inquire directly with Dell about this. You could also check with the Manufacturer of USB-C power adapters since they test their adapters with literally hundreds of devices. In particular, I would suggest checking with the company "Anker". They sell more USB-C adapters than probably anyone else and they should be able to tell you what works with your laptop.
As for the barrel to USB-C adapter you are looking at, I would not suggest it. It is rated for only 65W max, so, if it works at all it would be slow and a sub-optimal experience.
Same is true for the that power bank you were looking at.
Once again, Anker makes power banks that can supply a lot more power - I just got their latest yesterday that can supply 140W of power.
As for the maximum size of a power bank allowed on a plane, you are looking for a rating or 100WHh or less. Note that this is a different value than the number of watts that the adapter can supply.
Example: The Anker power bank I referenced can supply up to 140W, but the capacity it something like 89Wh, which is under the max allowable of 100Wh. Note that if the manufacturer does not supply a rating in Wh, look for a rating in terms of "mAh". The max allowable for this value is just over 27,000 mAh.
I realize that I'm throwing a lot of info at you, so please ask questions if you have any.
