The RCRP05B has about 5 Kbytes of memory for learned codes. The memory needed to learn a key varies with the quality of the learn, but a typical learn takes 25 bytes. So you may be able to get close to 200 learned keys before running out of memory.  Typically learning is not allowed to the Setup Key, the device keys, and sometimes the master power key. 

The files section in this forum has a CCF file for the DMR-E80H, and over at the best resource for UEI remotes www.hifi-remote.com/forums/, there is an upgrade file for a DMR-E95H.  In the File Section, one can download free tools which tell us what protocol, device numbers, and function numbers are used by the two similar model numbers.  (RemoteMaster and  DecodeCCF)

So it is easy (since I already have those tools loaded) to find out that a likely fit for your DMR-E100H is Panasonic protocol (no surprise there!), device 176 subdevice 0.  As you probably know, that is unfortunately also matches the Pany S29.  I surmise that your 100H is using the setting for Code 2 (subdevice 16) or Code 3 (subdevice 32) in order to avoid crosstalk between the two Panasonic devices.  Your  new remote probably doesn't have a setup code for those subdevices, although it has quite a few very new setup codes.

But there should be plenty of room for learning.  By the way, the DVD code is probably 0490.

The E100H will almost certainly have to be learned, because it is operating on an alternate code. I mentioned 176, but that is not a setup code, but rather the device number that the remote should send to the E100H along with a function number, and the subdevice number 16.

The 8300 usually works with Cable 1877.

The Teac may be a pain. Most Teac units use the NEC1 protocol, but it seems like each model uses a different device and subdevice number. So there are two issues: 1) what device/subdevice is used by the AG780, and 2) does the remote have a setup number that matches those numbers and has function numbers that fit.

I haven't seen any info on the ag780, but try Audio 2098 and 1074. Also 1077, 2169.

Mea culpa. I made two mistakes in describing the learning memory. The actual memory available for learning is 2K, and the Panasonic protocol takes 48 bytes per learn. I'm sorry about that.

Do you really need all of the E100H keys? We don't know which format the Teac uses, but if it is like most other Teacs, it will consume 24 bytes per learn, so you probably could fit most keys of both components.

Raptor said "If it had more memory I would buy at least two more even if they cost up to $10 more per remote. "

That really changes the picture. The RCRP05B is made by Universal Electronics, and they also make the remotes used by many cable companies, high end Vizio TVs, etc. Inside the battery cover is a 6 pin connector which can be used to load in all sorts of upgrades. There is a website devoted to these so-called JP1 remotes www.hifi-remote.com/forums/.   You can buy a USB cable for $35 shipped (or build one much cheaper).  The software is free.   If you manage more than one remote, the cost amortizes pretty quickly. 

With a JP1 cable, you can load in an upgrade to run the E100H without learnng any keys.  Such an upgrade frequently includes discrete functions which aren't available in the OEM remote.  For many components, the protocols, device numbers and function numbers are known (you can see them in the File Section at the above link, and a lot of the codes are available here).  So even if the dog ate the remote (as literally happened at my house!) you can still control the component.  Of course, not every component is known, e.g. your Teac.

However, using the original remote, you can learn the keys, and then download the learns into the computer.   The software decodes the learns into the protocol, device and function number, which is then loaded back into the remote in a much more compact format.  For example, the space required for a learn of one key of the E100H is 48 bytes, but when decoded the space needed is 2 bytes.  [Upgrade memory is in a different location than learn memory.  Macro memory is also in separate space.]

As an example, with the cable, it is easy to manage macros, and  change the delay time between steps in macros.

Thanks for the mention of the Teac setup code. Here's a couple of approaches to finding setup codes.

On the forum page of hifi-remote, near the top of the page, there is a heading for Lookup Tool. Using Device Search, and entering Audio 0463, you can see that it is NEC1 protocol, device 129, subdevice 115. 0463 is in 34 remotes, and the RCA isn't on the list. You can also check to see if some other setup code would work by using Protocol Search, and verify that the RCA has no NEC1 code with device 129. Of course with a cable you can put in a 129.115 upgrade. Actually you'd probably just use the AV G8500 upgrade that someone has posted in the File Section.

Using Brand Search, Scientific Atlanta would turn up 1877 among a lot of others. Or in the Files Section\Cable, the very first SA file listed is for the 8300 and includes "1877" in the description.