elementary differences: 

• DO executes a method or subroutine synchronous to your code
• JOB starts an asynchronous job in background

See onlinme docu how tp pass parameters
https://docs.intersystems.com/latest/csp/docbook/DocBook.UI.Page.cls?KEY=TCOS_DO
https://docs.intersystems.com/latest/csp/docbook/DocBook.UI.Page.cls?KEY=RCOS_cjob

I'd strongly recommend to use %Stream since 3.6 MB is huge for a String but not for a PDF.
Besides the absolute maximum of 3.6 MB for %String you may have additional limits of %String.
Dating from ancient ODBC the default max. for Strings is 50 !!!! If you don't set (MAXLEN="") explicitely

I assume you have a PatientID so you might be able to select your records using an INNER JOIN in this way:

SELECT <.......your columns....,contacttype,....> 
FROM my.patient as pat
INNER JOIN 
(select PatientID, MAX(DateFrom) as MaxDate FROM my.patient Group by PatientID) as max
ON  
pat.PatientID=max.PatientID AND pat.DateFrom=max.MaxDate
WHERE  <...whatever... >

so you get the records with the highest DateFrom by Patient
 

in order to provide efficient updates for DeepSee there is a feature named DSTIME.
It writes kind of a log about inserts, deletes, updates. This may suit your requirements.
About 2 years ago I have written an article about the subject. Take a look if this is what you need.
https://community.intersystems.com/post/synchronize-data-dstime
 

¡Hola @Kurro Lopez !
It's a really interresting issue.
#2) your second example can't work by principal as you don't pass a call parameter.
#1) It is not foreseen to use object properties as host-variables in SQL
The code fails in the generated Execute method.

set tResult = tStatement.%Execute($g(pObject.KeyProcess),$g(pObject.CodeSpecialist),$g(pObject.CodeProvider),$g(pObject.CodeCenter),$g(pObject.Date))

$GET for oblect-properties is just not ​implemented. It is definded by the class and always there,
But it is required and makes sense for multidimensional properties !

This is valid for ObjectScript as such and not related to SQL.​​​​​​
But in handwritten code you can use $g(NOTHING,pObject.KeyProcess) 
The generator just doesn't do it. 
 

Workaround #1: directly fiddle in the generated code .  Not recommended
Workaround #2:  move your properties with a helper function into local variables
and adjust your query to those variables 
example helper (with obj or id):
ClassMethod FillProp(pObject As Kurro.MyClass) As %Boolean [ SqlName = FILLP, SqlProc ]
{
if '$isObject(pObject) set obj=##class(Kurro.MyClass).%OpenId(pObject)
else  set obj=pObject
set %Kurro("kp")=obj.KeyProcess
     ,%Kurro("sp")= obj.CodeSpecialist
     ,%Kurro("pr")= obj.CodeProvider
     ,%Kurro("cs")= obj.CodeCenter
    ,%Kurro("dt")= obj.Date
quit 1
}
example query;
Query GetInfoRcc(objid As %Integer) As %SQLQuery(CONTAINID = 0, ROWSPEC = "IdList:%String,IdProcess:%String,Duration:%String")
{
    SELECT IdList, IdProcess, Duration
    FROM Kurro.MyClass
    WHERE KeyProcess = :%Kurro("kp")
    AND CodeSpecialist = :%Kurro("sp")
    AND CodeProvider = :%Kurro("pr")
    AND CodeCenter = :%Kurro("cs")
    AND "Date" = :%Kurro("dt")
   AND FILLP(:objid) = 1
}

works as expected.
Sorry for being late. I was interrupted by ....  15 times at least with nonsense
 

try:

;
set file=$system.Util.ManagerDirectory()_"messages.log"
open file:("RS"):1 w $T  open 2:99
try { for n=1:1 use file read lin use 2 write lin,! } catch { close 2,file  write n_" lines",! }
;

then use ^SPOOL mapping (OEX) to work on it with SQL

Mirroring is also available in Caché