Not sure if its been reported or not, but when using /give itemname 127, only 64 are given even though the oversized-stacksize: 127 is in config.yml.

/give item_name 16 does not recognize the new namespaceid's released in 1.13.x. I have to use /minecraft:give item_name 16 to get the appropriate block.

Results of ess version - ignore the version issue with EssentialsXExtras - this is known issue due to naming convention by that developer.
> ess version
[16:57:10 INFO]: CONSOLE issued server command: /ess version
[16:57:10 INFO]: Server version: 1.13.1-R0.1-SNAPSHOT git-Paper-225 (MC: 1.13.1)
[16:57:10 INFO]: EssentialsX version: 2.15.0.45
[16:57:10 INFO]: LuckPerms version: 4.2.88
[16:57:10 INFO]: Vault version: 1.6.7-b${env.TRAVIS_BUILD_NUMBER}
[16:57:10 INFO]: EssentialsXChat version: 2.15.0.45
[16:57:10 INFO]: EssentialsXExtras version: 2.15.0.1
[16:57:10 INFO]: EssentialsXProtect version: 2.15.0.45
[16:57:10 INFO]: EssentialsXGeoIP version: 2.15.0.45
[16:57:10 INFO]: EssentialsXAntiBuild version: 2.15.0.45
[16:57:10 INFO]: EssentialsXSpawn version: 2.15.0.45
[16:57:10 INFO]: Version mismatch! Please update all Essentials jars to the same version.

Steps to reproduce
First image shows the command offering 1 or 64 blocks, but not 127 as defined in config.

Result of command:

Autocomplete for /minecraft:give smmmadden oak_

Other plugins: I can provide exact versions if needed.
[17:02:21 INFO]: Plugins (51): AutoBroadcasterPlus*, AutoTorch, BungeeServerSigns*, BungeeTabListPlus*, ColorCodes*, CommandSync*, CorpseReborn*, CreativeGates*, CreeperHeal*, DeluxeJoin, DeluxeMenus*, DoorCloser*, dynmap*, EditableSign*, EnchantableBlocks, Essentials*, EssentialsAntiBuild*, EssentialsChat*, EssentialsExtras*, EssentialsGeoIP*, EssentialsProtect*, EssentialsSpawn*, HeadDatabase*, Jobs, Links*, LuckPerms*, LWC, MassiveBooks*, MassiveCore*, Missing_Recipes, OpenInv*, PacketListenerApi*, PlaceholderAPI, ProtocolLib*, PulseHealth*, QuickShop, Realistic-Swimming*, Residence, Ridables, SaneEconomy*, SecurityVillagers, SelectionVisualizer, SimpleSit*, Socket4MC*, TintHealth*, Vault*, Votifier, VotingPlugin, WorldBorder*, WorldEdit, WorldSystem

EssentialsX doesn't use namespaced item names because they are completely meaningless to the Bukkit API, which uses its own hardcoded material names. (Namespaced item names also predate 1.13.)

I would be surprised if oversized stacks still work on 1.13 - there was never a proper way to spawn them in, and Essentials's method likely broke with 1.13.

If there is anything I can help with, do let me know. Using /minecraft:give jungle_planks 127 gives 127 as expected.

Ignoring the tab suggestion, are you still able to run /give ... 127 to spawn an oversized stack?

nope - only gives 64

I don't believe Essentials plans to add support for namespaced IDs. In addition, I do believe that oversized stack size is not actually supported in 1.13+, which is why you do not see more than 64 spawned. To spawn 127, you will probably need to turn off oversized stacks (if you have not done so already).