What altitude to use for IFR off-airways route Say I want to fly off-airways (both Victor airways and T routes) for my IFR flight, direct to my destination in the US.  How do I know what my off-route altitude should be so I can file for that?
I would expect this would be an altitude above the OROCA and suitable for direction of flight, however I encountered this in the Instrument Procedures Handbook:

OROCAs are intended primarily as a pilot tool for emergencies and
SA. OROCAs depicted on en route charts do not provide the pilot
with an acceptable altitude for terrain and obstruction clearance
for the purposes of off-route, random RNAV direct flights in either
controlled or uncontrolled airspace. OROCAs are not subject to the same
scrutiny as MEAs, minimum vectoring altitude (MVAs), MOCAs, and other
minimum IFR altitudes. Since they do not undergo the same obstruction
evaluation, airport airspace analysis procedures, or flight inspection, they
cannot provide the same level of confidence as the other minimum
IFR altitudes.

This suggests we cannot trust the OROCA.  Then I suppose the 14 CFR 91.177 indicates I need to be at least 2000 ft above the highest obstacle within 4nm of my course in mountainous areas, or 1000 in non-mountainous areas.  But how do I know what this is without using OROCAs?  Do we check sectional charts, or is there something more practical?  Checking a sectional seems reasonable on the ground for filing, but not so if diverting in the air and flying direct to some other airport on an off-airway course not planed on the ground.
Thanks for any help!
This article covers the topic quite nicely

To begin with, a direct route will only be approved in a radar
environment. In many areas of the country this is not an issue. The
pilot, however, must be aware that filing an altitude at or near the
OROCA (Off-Route Obstruction Clearance Altitude) may not guarantee
radar coverage. In that case, the pilot should expect to be assigned a
different altitude or route.

Its also covered in this AOPA article a bit

If you plan a &quot;direct&quot; flight, point-to-point, follow the rules and
enter the correct equipment. For example, if &quot;/G&quot; (or &quot;slash Golf,&quot;
meaning that your airplane is equipped with an IFR-approved GPS and a
Mode C transponder) or &quot;/I&quot; (you have loran or VOR/DME and a Mode C
transponder) are not entered for these kinds of flights, the air
traffic control computer will reject your flight plan because that
route can't be flown with less capable equipment. Direct routing
requests also are approved only in a radar environment, so forget
about filing direct, off-airways when radar is not available, or in
areas of poor radar coverage.

So broadly speaking you can file the OROCA but ATC may issue a higher altitude for radar coverage reasons. I have also received direct routings en-route at previously filed altitudes if they meet the requirements. Where I fly its common for ATC to prefer an airway route to get you out of the terminal area but will generally clear you direct once in route.