The trial chat length is the same length as regular gameplay's, you just can't use all chat features so that bot accounts can't use trials to abuse/spam players.
You can usually fit about 3-4 decently-sized sentences in there. From my personal experiences, people generally post within one chat box, although heading into 2 or 3 does happen, especially with faster typers. If someone tried to throw multiple paragraphs into the chat, they might get some flack because all public chat goes into the same box. While you can filter the types, para-RP is best done in controlled spaces like a party, linkshell, or free company. Anything else would likely appear more like flooding.
IvikBlack on the RPC did code up a tool to help split longer posts into FFXIV-friendly copy and paste blocks. Even formatted for the appropriate channels. If you're looking to see how large your posts might be, it's a good tool for that.
http://www.rptoolbox.site/
edit to add on: Particular,y trial accounts cannot send a /tell (private message / whisper). They also cannot form parties, linkshells, or free companies, but can be invited into them, I think. If someone sent you a /tell, you'd have to likely publicly acknowledge that you received it. ...typically, most RP I've seen is done out in the open so this shouldn't cause an issue unless you're trying to work out details in private.
edit2: To not add a doublepost, you may enjoy these selected threads with some starter lore. (Classes and Jobs may contain spoilers. They should be labeled, but it's worth a preliminary warning!) I'd probably start with Units of Time and Measurement, as common Eorzean terms follow a renamed Imperial System for the most part. Geography and Settlements are helpful for backstory building, but may be a little bit of an info overload until you get more familiar with some of the common areas. It's also worth noting that a lot of people RP as without some sort of class/job designation. I'm sure WoW RP is/was similar in that battle mechanics are split from RP. There is no requirement to suscribe to any of the defined guilds, although they are certainly helpful if your character will be an adventurer, combatant of some form, gatherer, or artisan. (Likewise, there are a number of roles one can have that wouldn't apply to any of the in-game options and those are plenty fine too. I've only seen issues arise when someone tries to port a class/job/species/role from another setting into FFXIV and things do not line up.)
Eorzean Lore Starter Kit
-Racial Lore Compilation
-Class/Job Lore Compilation
-Hydaelyn Geography Lore
-Settlements in Eorzea Pre-Calamity
-Eorzean City-states' Political Structures Lore
-Eorzean Units of Time and Measurement Lore
What Year Is It? Time Passage in FFXIV
You can usually fit about 3-4 decently-sized sentences in there. From my personal experiences, people generally post within one chat box, although heading into 2 or 3 does happen, especially with faster typers. If someone tried to throw multiple paragraphs into the chat, they might get some flack because all public chat goes into the same box. While you can filter the types, para-RP is best done in controlled spaces like a party, linkshell, or free company. Anything else would likely appear more like flooding.
IvikBlack on the RPC did code up a tool to help split longer posts into FFXIV-friendly copy and paste blocks. Even formatted for the appropriate channels. If you're looking to see how large your posts might be, it's a good tool for that.
http://www.rptoolbox.site/
edit to add on: Particular,y trial accounts cannot send a /tell (private message / whisper). They also cannot form parties, linkshells, or free companies, but can be invited into them, I think. If someone sent you a /tell, you'd have to likely publicly acknowledge that you received it. ...typically, most RP I've seen is done out in the open so this shouldn't cause an issue unless you're trying to work out details in private.
edit2: To not add a doublepost, you may enjoy these selected threads with some starter lore. (Classes and Jobs may contain spoilers. They should be labeled, but it's worth a preliminary warning!) I'd probably start with Units of Time and Measurement, as common Eorzean terms follow a renamed Imperial System for the most part. Geography and Settlements are helpful for backstory building, but may be a little bit of an info overload until you get more familiar with some of the common areas. It's also worth noting that a lot of people RP as without some sort of class/job designation. I'm sure WoW RP is/was similar in that battle mechanics are split from RP. There is no requirement to suscribe to any of the defined guilds, although they are certainly helpful if your character will be an adventurer, combatant of some form, gatherer, or artisan. (Likewise, there are a number of roles one can have that wouldn't apply to any of the in-game options and those are plenty fine too. I've only seen issues arise when someone tries to port a class/job/species/role from another setting into FFXIV and things do not line up.)
Eorzean Lore Starter Kit
-Racial Lore Compilation
-Class/Job Lore Compilation
-Hydaelyn Geography Lore
-Settlements in Eorzea Pre-Calamity
-Eorzean City-states' Political Structures Lore
-Eorzean Units of Time and Measurement Lore
What Year Is It? Time Passage in FFXIV